fuel. Question. Additive. Question.

It helps but EPA requires detergent additives. If you buy TopTierGas.com (big guys like Shell/Chevron) they have put even more than the minimum amount. After that one detergent is as good as the next, as far as we know. I try to use TopTierGas.com but my area that's easy....we have mostly the major brands.

I was just noticing recently my gaso in my mower gas can was really smelly, I am wondering if that was trace sulfur or maybe the additive stinks...not sure. I am looking for the least smelly next time. I have a hunch the smelly batch came from Shell but I am not sure.

 

If you strike a match to a puddle of it and it lights on fire, I'm good to go.

 

There are a list of ethanol free gas stations listed by state at pure-gas.org.

 

Wow, this is a 5 year old thread.
Just for anyone's information in the 5 years since this thread, I've gotten over my paranoia about the Prius recommended octane.

I run regular 87 grade almost all the time. And no problem. Occasionally I run a tank of premium or run a tank with a Techron treatment. But for normal operation most of the time I would highly recommend "regular".

 

This ad is interesting:
76® Gas-Our Gas

Its says Top Tier is 2.5x more than EPA minimum amount of detergent.
Phillips76 says they are putting 3x in theirs. They say 5 tankfuls needed to see difference over EPA minimim required detergent level.

 

87 regular and getting great gas mileage in the 60s...but the performance on Hills is laughably bad, considered it was just something to live with when it comes to the Prius. Nice to know 89 Octane helps with Hill climbs, because I'm thinking of taking mine on long driving trips to Colorado and Utah soon (from Texas), and was worried about climbing up Mountains with a loaded up Prius.

 

Design of the piston top and fuel delivery along with the Atkinson design of this engine make the 13-1 compression ratio possible without the detention problem with high compression engines of the past. Using a higher octane rated fuel than recommended in the user manual is a complete waste of money. But how we insist to ourselves that what we read on the web is more accurate than the engineers that designed the vehicle will always win out in certain crowds.

 

If you know what predetonation (pinging) is....and if you can detect it.....then you're one of the few people who need to use a higher octane fuel than the owner's manual calls for.

For others?
The good news is that spending more money on your gas than you have to won't really hurt the car.

YMMV

 

Actually, the 13-1 compression (expansion ratio) ratio on the Prius engine is somewhat of a misnomer. On paper the compression ratio is basically correct from the standpoint of cylinder volume and stroke. However, the valve timing on this engine changes all of that. The full intake stroke(the full length) draws in the A/F mixture but on the way back up on the compression stroke the intake valve remains open for a miniscule amount of time, pushing a portion of the fuel mixture back into the intake. With fancy valve timing this basically shortens the stroke of the engine on compression. The result of this is about an 8-1 compression ratio. So, the use of higher octane fuels is not really necessary.