# ATTN: Routan SEL owners, what fuel octane do your regularly use?



## tipoytm (Nov 16, 2009)

Hi Everyone,
Happy to be a new Routan SEL owner! I'd like to take a poll on what you guys regular use for fuel, *87oct vs. 89oct*. The manual states that you can use 87 oct, but it recommends 89oct on the 4.0L engine. If you have tried both, I'd love to hear any feedback (ie. if you feel any noticeable difference, etc.). I regularly gas up at Costco cuz they have the cheapest gas, but I don't think they serve 89oct (only 87 and 91). I was even thinking of using Costco's 91oct instead since it would be the same price as 89oct on most of the other gas stations. Thoughts?

_Modified by tipoytm at 11:27 AM 11-16-2009_


_Modified by tipoytm at 11:50 AM 11-16-2009_


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## troop94 (Jul 13, 2009)

*Re: ATTN: Routan SEL owners, what fuel octane do your regularly use? (tipoytm)*

I have the SEL 4.0 and always use regular (the lowest octane). I've never had the slightest problem and it shouldn't reduce your horsepower (unlike certain premium-recommended engines). As you change octanes, the engine computer detects what octane you are using and adjust the spark timing accordingly.


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## tipoytm (Nov 16, 2009)

I'm aware that the ECU detects the octane you put into the Routan, and adjusts accordingly... but there's a reason why the manual recommends higher octane fuel. I would like to get the best possible performance/fuel-economy ratio on the minivan, that's why I believe it's worth it to go with 89oct, even with the 10cent price difference. Still, I'd love to hear everyone's opinion on this subject.


_Modified by tipoytm at 12:03 PM 11-16-2009_


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## early74B (Feb 18, 2009)

*Re: (tipoytm)*

I'm using 89 in my SEL as well to maximize fuel mileage, my Routan is at 4K miles now and on long trips I've been pleased with the highway mileage (avg is about 25+, max has been 27+) --- now is it due to simply the gear ratio of the trans at high speeds or the combo of octane, etc. -- I don't know but you probably could due something analytical with how much more cost of fuel versus MPG change. The only problem being is you would have too many variables unless you drove the same loop, at the same speed, weather conditions, load, etc., etc. -- why not simply use what the VW engineers have come up with? I have noticed that my around town mileage has been getter better the more miles I've put on it (around 18+ now, up from 17).


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## troop94 (Jul 13, 2009)

*Re: (early74B)*

"there's a reason why the manual recommends higher octane fuel"
I'm highly skeptical it makes financial sense to pay for high octane gas for this particular engine. But, to each his own.


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## tipoytm (Nov 16, 2009)

I've researched this subject before, about engines/ECUs and how different fuel octanes affect performance/fuel economy. Sure the 4.0L engine can run both 87 and 89 octane with no issues, but the ECU uses different timing maps for each. The more optimal map will of course be 89, where timing advance will be a few more degrees higher than 87oct... (Correct me if I'm wrong) which in turn translates to a bit more horsepower/torque while maintaining roughly the same amount of fuel consumed (given the same throttle %). 
In short, an engine's combustion efficiency & energy output is more optimal for the higher octane fuel (89 in this case) if the ECU has different tunes for each. 


_Modified by tipoytm at 9:44 AM 11-19-2009_


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## PASSAT2001.5 (Apr 8, 2001)

*Re: (tipoytm)*

hm... I've been using 93 since since march, and still have not broke 4K miles yet. Hope I am not over feeding.


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## tipoytm (Nov 16, 2009)

Nah, it's not overfeeding... if you use 91 or 93 octane on the 4.0L engine, it's not going to be any more beneficial than the recommended 89 octane since the ECU won't have a more advanced timing map for it. Basically, you are just paying extra for better gas with no additional benefit. Stick with 89 and save the extra $$.


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## redzone98 (Jun 10, 2004)

*Re: (tipoytm)*


_Quote, originally posted by *tipoytm* »_
Stick with 89 and save the extra $$.


id imagine that the engine map is just a fraction more aggressive than the 3.8L, so in some small percentage of the population will get pre-ignition if running regular...
so to cover their asses, Chrysler bumped the Octane up a few points. but id bet that <5000ft elevation you can run regular no problems.


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## tipoytm (Nov 16, 2009)

*Re: (redzone98)*

^ Still, we don't know what the timing maps look like till we see the actual tables. I'd rather spend 10cents more per gallon just to have that peace of mind that the engine is running at it's optimal ignition timing (no pre-ignition/knocks). I'll even switch to Synthetic oil after the VW 3-year maintenance has expired.


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## 71sbeetle (Apr 12, 2002)

*Re: (tipoytm)*

we've been using both (you can see on our fuelly.com page) and we don't feel a difference in power, nor do we get a difference in gas mileage


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## routancan (Aug 8, 2009)

*Re: (71sbeetle)*

Strictly using 87 octane...according to the readout in the van, we average around 13L/100km, or 18mpg with combined city/highway driving. 
Best mileage we have experienced is 9L/100km or a shade over 26mpg on the highway. http://****************.com/smile/emthup.gif


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## Denarae (11 mo ago)

tipoytm said:


> I'm aware that the ECU detects the octane you put into the Routan, and adjusts accordingly... but there's a reason why the manual recommends higher octane fuel. I would like to get the best possible performance/fuel-economy ratio on the minivan, that's why I believe it's worth it to go with 89oct, even with the 10cent price difference. Still, I'd love to hear everyone's opinion on this subject.
> 
> 
> _Modified by tipoytm at 12:03 PM 11-16-2009_


I have had this Routan SEL for nearly 2 years. The 87 - 89 octane is not the issue. I have gotten 24 mpg with my van and it has dropped mpg too fast. I guess I need to hook it up to a computer. Possibly the EGR unit is the culprit. They are expensive. Can they be cleaned? It so, how? I just spent $642.00 on a new key($242) programming($99.00) and tow to the dealer (285.00). Totally way out of proportion. Please let me know about the EGR and other possibilities. Thank you.


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