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    Thread: What octane should I run with Jetta 2.5?

    1. Junior Member
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      03-10-2013 10:39 PM #1
      Hello. My girlfriend just bought her first Volkswagen. She was able to manage to buy a leftover 2012 Jetta SE with convience and sunroof. I was wondering what octane fuel is best to run and if running 87 is horrible for it or not. And if anyone had any ideas to if running higher octane gives better MPG.

      Thanks

    2. Member LWW's Avatar
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      03-10-2013 10:52 PM #2
      Quote Originally Posted by Zerdio View Post
      Hello. My girlfriend just bought her first Volkswagen. She was able to manage to buy a leftover 2012 Jetta SE with convience and sunroof. I was wondering what octane fuel is best to run and if running 87 is horrible for it or not. And if anyone had any ideas to if running higher octane gives better MPG.

      Thanks
      What has been proven is:

      - The car will not have drveabilty issue on 87 octane.

      - There is a few horsepower to be gained by running on 93 octane

      I have ran a few tank of both and the results have been 24.87 MPG on 93, 25.50 on 87, and 25.35 on 89.

      That's a very sall sampling on a new engine through winter ... but enough to suggest that there is no significant difference in MPG between the three.

    3. Member mvthree's Avatar
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      03-10-2013 10:54 PM #3
      Quote Originally Posted by Zerdio View Post
      Hello. My girlfriend just bought her first Volkswagen. She was able to manage to buy a leftover 2012 Jetta SE with convience and sunroof. I was wondering what octane fuel is best to run and if running 87 is horrible for it or not. And if anyone had any ideas to if running higher octane gives better MPG.

      Thanks
      Run 87. I've used 93 and it really doesn't change much the only way you'd really benefit is if you get the ecu programmed to run a higher grade. Typically high performance and turboed cars use higher grade fuel.

      Also for your cars in the future the recommended fuel is listed in the manual

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      03-10-2013 10:55 PM #4
      Quote Originally Posted by Zerdio View Post
      Hello. My girlfriend just bought her first Volkswagen. She was able to manage to buy a leftover 2012 Jetta SE with convience and sunroof. I was wondering what octane fuel is best to run and if running 87 is horrible for it or not. And if anyone had any ideas to if running higher octane gives better MPG.

      Thanks
      Do what the owners manual says.
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      03-10-2013 11:01 PM #5
      Quote Originally Posted by mvthree View Post
      Run 87.

      Also for your cars in the future the recommended fuel is listed in the manual
      This. The engineers didn't guess that 87 would be ok. They built the engine and ECU specs to support NA fuels. If it required a higher octane (again, please don't confuse fuel QUALITY with octane rating), they would specify PREMIUM/91+ like on the GLI.
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      03-10-2013 11:18 PM #6
      Quote Originally Posted by adamkramerusn View Post
      This. The engineers didn't guess that 87 would be ok. They built the engine and ECU specs to support NA fuels. If it required a higher octane (again, please don't confuse fuel QUALITY with octane rating), they would specify PREMIUM/91+ like on the GLI.
      Quote Originally Posted by MikeMeachum View Post
      Will there be a Jetta/ GLI VII thread? I got one.

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      03-10-2013 11:41 PM #7
      Quote Originally Posted by LWW View Post
      What has been proven is:

      - The car will not have drveabilty issue on 87 octane.

      - There is a few horsepower to be gained by running on 93 octane

      I have ran a few tank of both and the results have been 24.87 MPG on 93, 25.50 on 87, and 25.35 on 89.

      That's a very sall sampling on a new engine through winter ... but enough to suggest that there is no significant difference in MPG between the three.
      Good 2 know others had similar experience as I had. I continue to run 87.
      When I signal, I'm advising you that I'm about to change lanes, not asking for you to speed up and stop me!

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      03-11-2013 12:20 AM #8
      Regular all the time


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      03-11-2013 07:09 AM #9
      Well the dealer never gave us the owners manual and I keep forgetting to ask but while I'm typing I am going to make a note of it ha. But I just wanted to see what everyone though if this subject. But I'm sure my girlfriend will be happy to know she can still buy cheap gas!!

    10. Member LWW's Avatar
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      03-11-2013 07:12 AM #10
      Quote Originally Posted by adamkramerusn View Post
      This. The engineers didn't guess that 87 would be ok. They built the engine and ECU specs to support NA fuels. If it required a higher octane (again, please don't confuse fuel QUALITY with octane rating), they would specify PREMIUM/91+ like on the GLI.
      Actually ... they used a knock sensor so that it could run on 87.

      Most, and probably all, cars tat run on 87 will pick up some power ith higher octane.

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      03-11-2013 02:56 PM #11
      I run 89 Octane in mine and always get my gas at reputable gas stations.. A car can benefit from a higher fuel octane, but this engine doesn't need the highest. It doesn't hurt to run mid-grade, that's for sure.. And if it hurts your wallet, you shouldn't be driving a brand new car to begin with.

    12. Member LWW's Avatar
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      03-11-2013 04:19 PM #12
      Quote Originally Posted by dunndarryn View Post
      I run 89 Octane in mine and always get my gas at reputable gas stations.. A car can benefit from a higher fuel octane, but this engine doesn't need the highest. It doesn't hurt to run mid-grade, that's for sure.. And if it hurts your wallet, you shouldn't be driving a brand new car to begin with.
      It depends on what you want ... if it's economy, brand name 87 will work well.

      If you want a relatively cheap power mod that won't cause warranty issues ... 93 will work.

      That being said, I plan to do some additional tanks on all 3 in warmer weather, but the 89 has potential as the best compromise between the two concerns.

      I'm a heavy footed old school hot rodder ... but this is my adult car.

    13. Member jmchristian's Avatar
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      03-11-2013 04:48 PM #13
      Quote Originally Posted by LWW View Post
      Actually ... they used a knock sensor so that it could run on 87.

      Most, and probably all, cars tat run on 87 will pick up some power ith higher octane.
      From everything that I have read or been told, your statement is wrong. An engine that is made to run on 87 octane will run the best on 87 octane.

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      03-11-2013 05:38 PM #14
      Quote Originally Posted by LWW View Post
      Actually ... they used a knock sensor so that it could run on 87.

      Most, and probably all, cars tat run on 87 will pick up some power ith higher octane.
      Very little power is to be gained, but a lot more deposits in the combustion chamber from using higher octanes (even Top Tier). The ECU does not advance the timing enough to fully support higher octanes, especially 91+
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    15. Member MK611's Avatar
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      03-11-2013 06:26 PM #15
      Quote Originally Posted by BsickPassat View Post
      Very little power is to be gained, but a lot more deposits in the combustion chamber from using higher octanes (even Top Tier). The ECU does not advance the timing enough to fully support higher octanes, especially 91+
      Can I get some advice to this? I've put regular Shell 87 in my 2.5 all the time ever since I picked up the car. The dealer even filled Shell since Day 1. A while back I decided to put Chevron (same price as I usually fill up with Shell) and noticed horrible gas MPG. Same full tank driving I did with the Shell fuel lasted me max a week. Same driving, full tank with Chevron, half a week.

      Any insight?

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      03-11-2013 06:40 PM #16
      I ran 93 with no problems at all in my mkv for 89k miles with absolutely no problems.

      On 15k in the vi and still zero issues. Idles smooth, drives great.

    17. Member LWW's Avatar
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      03-11-2013 07:49 PM #17
      Quote Originally Posted by jmchristian View Post
      From everything that I have read or been told, your statement is wrong. An engine that is made to run on 87 octane will run the best on 87 octane.
      Magazine dyno testing has been done on this topic ... including the VW 2.5 ... and modern engines rated for 87 will produce more powet on highet octane.

      That's why knock sensors are used ... if the vehicle was designef to run optimally on 87 no knock sensor would be needed. The reality is they are designec to run minimally on 87.

    18. Member jmchristian's Avatar
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      03-11-2013 08:38 PM #18
      Why TOP TIER

      The intention of the TOP TIER Detergent Gasoline standards is to create a winning situation for gasoline retailers, auto manufacturers and drivers. Currently, many gasoline retailers provide fuels with lower-quality additive packages that can build up deposits on fuel injectors and on intake valves. Others can build up deposits in combustion chambers and may lead to intake valve sticking. These lower levels of additives can have negative impacts on engine performance and vehicle responsiveness.

      If you are worried about deposits it doesn't matter what grade of gas you use. But like I said before buying premium grade gas for the 2.5 engine is a total waste of money. The grade you should use for your VW is located on the inside of the fuel filler flap. But if you have a modified chip disregard everything.

    19. Member itskohler's Avatar
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      03-11-2013 08:53 PM #19
      Quote Originally Posted by jmchristian View Post
      Why TOP TIER

      The intention of the TOP TIER Detergent Gasoline standards is to create a winning situation for gasoline retailers, auto manufacturers and drivers. Currently, many gasoline retailers provide fuels with lower-quality additive packages that can build up deposits on fuel injectors and on intake valves. Others can build up deposits in combustion chambers and may lead to intake valve sticking. These lower levels of additives can have negative impacts on engine performance and vehicle responsiveness.

      If you are worried about deposits it doesn't matter what grade of gas you use. But like I said before buying premium grade gas for the 2.5 engine is a total waste of money. The grade you should use for your VW is located on the inside of the fuel filler flap. But if you have a modified chip disregard everything.
      UM tuned.

    20. Member LWW's Avatar
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      03-11-2013 08:58 PM #20
      Quote Originally Posted by jmchristian View Post
      Why TOP TIER

      The intention of the TOP TIER Detergent Gasoline standards is to create a winning situation for gasoline retailers, auto manufacturers and drivers. Currently, many gasoline retailers provide fuels with lower-quality additive packages that can build up deposits on fuel injectors and on intake valves. Others can build up deposits in combustion chambers and may lead to intake valve sticking. These lower levels of additives can have negative impacts on engine performance and vehicle responsiveness.

      If you are worried about deposits it doesn't matter what grade of gas you use. But like I said before buying premium grade gas for the 2.5 engine is a total waste of money. The grade you should use for your VW is located on the inside of the fuel filler flap. But if you have a modified chip disregard everything.
      +5 HP ... +12 LB/FT torque with 91 octane over 87 octane.

      http://www.europeancarweb.com/tech/p...n/viewall.html

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      03-11-2013 10:13 PM #21
      Quote Originally Posted by MK611 View Post
      Can I get some advice to this? I've put regular Shell 87 in my 2.5 all the time ever since I picked up the car. The dealer even filled Shell since Day 1. A while back I decided to put Chevron (same price as I usually fill up with Shell) and noticed horrible gas MPG. Same full tank driving I did with the Shell fuel lasted me max a week. Same driving, full tank with Chevron, half a week.

      Any insight?
      Could be a bad tank.

      Chevron.... they are the ones that invented the popular PBA detergent used in inferior gasolines.

      They also developed the PEA detergent used in many Top Tier gasolines.

      Combustion chamber Deposits with using higher octane... is a long term issue, where that over time, due to incomplete combustion, deposits will form, which will increase the compression ratio, and thus necessitate more aggressive cleaning additive.
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      03-11-2013 10:17 PM #22
      Correct me if im wrong, carbon build up is more prevalent in direct injection engines.

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      03-11-2013 10:19 PM #23
      Quote Originally Posted by itskohler View Post
      Correct me if im wrong, carbon build up is more prevalent in direct injection engines.
      You are correct
      Quote Originally Posted by MikeMeachum View Post
      Will there be a Jetta/ GLI VII thread? I got one.

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      03-11-2013 10:20 PM #24
      Quote Originally Posted by itskohler View Post
      Correct me if im wrong, carbon build up is more prevalent in direct injection engines.
      it happens in port injection.

      unlike direct injection, it can be treated with gasoline additives, or use a good fuel that uses PEA detergent.

      Last edited by BsickPassat; 03-11-2013 at 10:25 PM.
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      03-11-2013 10:21 PM #25
      Quote Originally Posted by itskohler View Post
      Correct me if im wrong, carbon build up is more prevalent in direct injection engines.
      Correct, because there isn't fuel being sprayed on the backside of the valves in the air/fuel mixture as it enters the cylinders.
      '12 Jetta GLI Platinum Gray

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      03-11-2013 10:26 PM #26
      Quote Originally Posted by adamkramerusn View Post
      Correct, because there isn't fuel being sprayed on the backside of the valves in the air/fuel mixture as it enters the cylinders.
      I knew why, just letting nyquil take its effectscand not tying to think too hard.

      Ive seen a torn down 2.5 at 100k and it looked relatively good when compared to a tsi with slightly less mileage on the forums.

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      03-12-2013 04:13 PM #27
      How do I prevent carbon buildup in a 2.0 turbo direct injected engine? Right now I use Marathon 93.

    28. Member jmchristian's Avatar
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      03-12-2013 04:14 PM #28
      Quote Originally Posted by LWW View Post
      +5 HP ... +12 LB/FT torque with 91 octane over 87 octane.

      http://www.europeancarweb.com/tech/p...n/viewall.html
      I can't argue with that.

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      03-12-2013 04:57 PM #29
      Quote Originally Posted by LWW View Post
      +5 HP ... +12 LB/FT torque with 91 octane over 87 octane.

      http://www.europeancarweb.com/tech/p...n/viewall.html
      The argument here, and the OP's question, what whether or not he should run 87.... not about peak HP gains with better fuel. Are going to notice the extra 5hp during normal driving on your daily communte? Hell no. 12 ft/lbs of torque is a nice bump, but again... would you notice it in a blind test? Probably not. Then there's the cost. Will you be driving at full throttle all the time to take advantage of the timing.... again, No. If you want to have a track day your 2.5L, or just want to do some 'spirited' driving, have at it. In the end you're just wasting your money with the higher octane fuels on that engine. Stick with top tier fuels, do your scheduled maintenance, and enjoy your 5 cylinder.
      Last edited by adamkramerusn; 03-12-2013 at 05:00 PM.
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    30. Member ChefBlake's Avatar
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      03-12-2013 05:13 PM #30
      Go green and run B100!

    31. Member LWW's Avatar
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      03-12-2013 06:40 PM #31
      Quote Originally Posted by adamkramerusn View Post
      The argument here, and the OP's question, what whether or not he should run 87.... not about peak HP gains with better fuel. Are going to notice the extra 5hp during normal driving on your daily communte? Hell no. 12 ft/lbs of torque is a nice bump, but again... would you notice it in a blind test? Probably not. Then there's the cost. Will you be driving at full throttle all the time to take advantage of the timing.... again, No. If you want to have a track day your 2.5L, or just want to do some 'spirited' driving, have at it. In the end you're just wasting your money with the higher octane fuels on that engine. Stick with top tier fuels, do your scheduled maintenance, and enjoy your 5 cylinder.
      The reply you quoted was to another question.

      If you look at my earlier post the OP's concern was addressed.

    32. n00b
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      07-19-2013 12:08 PM #32
      I changed over from 87 with 10% ethanol (which is what most pumps have) to 91 that is 100% gasoline with no ethanol added and it has made a huge impact in my performance and mileage (BP brand by the way). Mileage has increased by 4 mpg and I hit 36 + mpg on the highway consistently.

      I think it has more to do with the lack of ethanol than the octane level. Most stations don't carry 100% gasoline so you'll have to search for it. Luckily I have one in my town that does.

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      07-19-2013 07:23 PM #33
      Premium since day one. Cry about it.

      Delivered by GS4.

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      07-19-2013 08:52 PM #34
      87 all day everyday, it's a jetta, not a porsche.

    35. 07-20-2013 12:00 PM #35
      I just run regular because that's what the manual says.
      @WhiteOnRice25

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