visatrade

I did a quick search on the forums. I am surprised I did not find anything on this issue. My question is, I noticed on the inside of my gas tank door it "Recommends" premium. However, it should be noted my v6 AFC engine is non-turbo and should not be considered "High Performance."

Will 91 octane give my engine longer life? The engine has over 150,00 miles on it as well. I do not have an owners manual yet so, I am not completely sure if I need to be putting supreme in. I know that hydrocarbons increase with higher octane which could clog the catalytic converters but, I plan on removing my cats soon since I passed smog.

I would greatly appreciate a few replies before this thread goes cold since supreme is twenty cents more per gallon than regular in California and would save me $2.80 at the pumps per fill-up.

Rusty Spokes

IMHO premium is the way to go. Our AFC engines since 12-94 (10.3 to 1 in prior years) have a 10 to 1 compression ratio with knock sensors. Using a higher octane fuel will allow the engine management system to operate at the optimal programmed range for power and efficiency. Hydrocarbons don't really increase with high octane fuel..the O2 sensors control that.

If you fill up once a week@$2.80 the additional cost is $145 a year.

visatrade

Thank you for your response Rusty Spokes. I am concerned with the longevity of the engine. $145 a year is 2 new tires in my world. If it is true higher octane will increase engine life as well as better performance I am sold.

As far as I can tell in higher octane is required in vehicles with higher compression. A Honda civic D16Vtec runs 9.2 to 1 compression ratio my Rx7 N/A has a 9.7 to 1 compression ratio. However, a LS1 (Corvette) engine has a compression ratio of 10.1 to 1 and should probably run premium. But I had a Mitsubishi Eclipse GSX with a 4g63 engine. I guess the compression ratio on that is very low like 7.1 to 1 but they say static. Maybe for the turbo?

I just noticed similar threads. This is a good link https://www.audiworld.com/forums/a4-...m-gas-2901013/ I am not sure if the b9 has a turbo or whatever.

They mention Performance as well and let it be stated I drive like a grandma. I rarely push my cars only when I am extremely frustrated which happens maybe once or twice a month and only for a brief period (I.e. Traffic signals giving me all reds for 2 miles). I used to drive backroads but gave that up long ago because I cannot afford simple maintenance such as brakes, suspension, and tires.

jnsluft

The manual for my '95 Cabriolet specifies premium unleaded. I assume yours would also.

yakimatdi

Another concern is the use of ethanol in an old engine. I use premium ethanol-free in our '97 cab because we drive it only on weekends from April through October. I add fuel stabilizer for the winter sleep, but I don't want water vapor buildup during the rest of the year either. Also, I'm not sure if those '97 seals like ethanol.

Rusty Spokes

I doubt that running regular grade fuel will damage our 12v V6 engines. The engine management system with knock sensors and adaptive programming will adjust for a lower quality fuel. The downside is the engine performance and fuel economy will suffer. There is the price vs cost equation. If you get 2-3 more MPG and spend .25 cents more per gallon at the pump, what is the return? Could be a break even.

I have had some concerns about ethanol in my older cars/motorcycles. I use Marvel Mystery Oil as an additive in the fuel. About 4oz per 10 gallons. No ethanol related problems.

CRAZY_RUSSIAN

while we are on the topic of fuel, what would help to pass emissions? someone sugested adding 10% of ethanol to the fuel. open for sugestions guys

Rusty Spokes

Get the tank near empty and find a gas station that sells E85 and add a few gallons..then drive to the emission testing store and do your test. Chances are your NOX has caused problems passing in the past. E85 will knock the NOX numbers way down. Don't drive around too much with E85.

Once done..go top off the tank with some good hi-test 93 fuel and get some corn tacos to celebrate.

Nevada E85 Gas Station Locations

CRAZY_RUSSIAN

last time i tried to pass, I was too high on HC. but welding new cats here in a few days. anyways, just in case if new cats don't get me by, was gonna look into other options.
so would you say 50/50 mix of E85 and regular?
also, no idea where i can get 93 in this town :-(

egp320i

Not sure about you guys but I only have either 87 or 91, 89 might be the middle ground if available.
I've ran both, it does appear 91 give you a nip more MPG, I can't really tell about any power increase though.