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View Full Version : 87 octane vs. 91 octane?


jhu
02-24-2009, 02:20 PM
My wife's Passat has the 1.8T engine in it. The manual states that 91 octane should be used, but 87 can be used with slightly decreased performance. I figure that as long as the rpms are in a range that don't give any significant boost, it should be okay to use 87 octane. What are people's thoughts on this?

abcdpeterson
02-24-2009, 04:42 PM
Does the manual actualy state
that 91 octane should be used, but 87 can be used with slightly decreased performance.

if the manual says you can use 87, I would try using 87. I would think the knock sensor should adjust the timing for 87.
if your hyper miling the performance is likly not an issue.

jkp1187
02-24-2009, 04:50 PM
Knock sensor should adjust the timing. Still, I'd steer clear just because if performance may suffer, fuel economy may suffer, too. (Also, knock retard notwithstanding, I'd be ultra-conservative with a turbo engine - if 91 is recommended, run 91 in it.)

2008 Civic Hybrid
02-24-2009, 08:38 PM
I owned a Passat 1.8T for 6 years before changing to a Hybrid.

I think the VW Passat 1.8T called for 91 RON. Not 91 Octane.

See here... http://www.type2.com/bartnik/octane.htm

Hope this helps.

jkp1187
02-24-2009, 10:18 PM
The EPA (fueleconomy.gov) says that a Passat with the 1.8T takes premium gasoline.

drimportracing
02-24-2009, 10:20 PM
I would use 87 for normal driving and 91 for boosted, thrill seeking, law breaking, pee in your pants, hide the kids and animals, I think he is gonna wreck kind of driving.

I'm a bit of a daredevil though, I get my thrills from opening cereal boxes upside down and getting the prize first, I'm wild like that! - Dale (only thing boosted on my car is the tire pressure.)

drimportracing
02-24-2009, 10:24 PM
The EPA (fueleconomy.gov) says that a Passat with the 1.8T takes premium gasoline. Was that the EPA (evil petroleum assistants) when Bush owned the government or when he was replaced by a man with a soul? (rhetorical) - Dale

hogrod
02-24-2009, 10:48 PM
In my state they have to mark gasoline that contains ethanol, 95% of stations I have used both regular and mid grade are 10% ethanol but premium fuel doesn't have any.

My car only calls for regular 87oct., but because of the ethanol It has I get much worse mileage running cheap gas. Another nice side effect, the car seems to have much better throttle response with premium.

PILL
02-24-2009, 11:59 PM
In my state they have to mark gasoline that contains ethanol, 95% of stations I have used both regular and mid grade are 10% ethanol but premium fuel doesn't have any.

My car only calls for regular 87oct., but because of the ethanol It has I get much worse mileage running cheap gas. Another nice side effect, the car seems to have much better throttle response with premium.

I think it is just in your head. 91 has no more power than 87, it actually resists burning more.

hogrod
02-25-2009, 02:03 AM
I think it is just in your head. 91 has no more power than 87, it actually resists burning more.


I'm pretty sure I said that with higher octane I notice better throttle response, not that it made more power. I assume this is because the computer is adjusting the timing differently when running the higher octane fuel, as most newer cars will do.

Notice I never specifically said 91 octane? That's because only a few stations around here carry that octane level of premium fuel. Most stations here are 87, 89, & 93 octane for the three levels of fuel.

Also you missed the most important thing I stated, that only the premium fuel around here doesn't contain ethanol. I loose 5mpg or more just running a 10% blend, so Premium is well worth the extra couple dollars per tank.

Kurz
02-25-2009, 05:36 AM
Use 87 but keep an eye on Fuel Economy and Subtle changes.

ALS
02-25-2009, 12:56 PM
Ever thought of using 89 octane instead of 87. My manual says to use 91 or higher. Yet 89 octane gets me the same gas mileage as 91-93 in my 740 Turbo. Both cars run fine on 89 and the 960 does get a little better mileage with 91-93. BTW both my cars require premium and they run like absolute garbage with 87 octane. Gas mileage drops like a rock and have a major decrease in HP with 87 in the tank.

jkp1187
02-25-2009, 09:51 PM
Was that the EPA (evil petroleum assistants) when Bush owned the government or when he was replaced by a man with a soul? (rhetorical) - Dale

Non-sequitur. Government officials have no souls.

(Rhetorical.)

99LeCouch
02-28-2009, 01:28 PM
I'd use the 91 or 93. If you ever need to get into boost it won't kill the engine.



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