Top tier gas : Healthier for your car ...

[iA_b4_07HB]

Owners manuals from Toyota now all recommend Top Tier gas. The original standard for detergency levels was based on a very very early, not very demanding, BMW injection system, and was based on the relatively short emissions compliance period in non-California (and California compliant) states. I have never noticed any difference in mileage from any gasoline except E10 vs. "just gas".

I HAVE noticed smoother operations with midgrade or premium fuel. If your engine runs on premium in Europe, the odds are it will run better on premium over here. This is because modern ECM (engine control modules) are adaptive in terms of tuning to the fuel used. I think anything with a compression ratio over 9.5 to 1 will benefit; the knock sensor will kick in later and you'll get a little more power and a smoother driver experience. Also, most premium fuels include twice the detergents of regular.

Costco and Arco are both currently Top Tier, and are the ones I try to buy, since they are cheaper. Valero certainly isn't a budget gas, but they are Top Tier these days. Kwik Serve is no longer Top Tier IIRC.

[Captain Yaris]

Originally Posted by iA_b4_07HB

I HAVE noticed smoother operations with midgrade or premium fuel. If your engine runs on premium in Europe, the odds are it will run better on premium over here. This is because modern ECM (engine control modules) are adaptive in terms of tuning to the fuel used. I think anything with a compression ratio over 9.5 to 1 will benefit; the knock sensor will kick in later and you'll get a little more power and a smoother driver experience. Also, most premium fuels include twice the detergents of regular.

Costco and Arco are both currently Top Tier, and are the ones I try to buy, since they are cheaper. Valero certainly isn't a budget gas, but they are Top Tier these days. Kwik Serve is no longer Top Tier IIRC.

I thought maybe I was just crazy, but my experience has been the same. I definitely feel as if the engine runs smoother. I’m not sure that I get a noticable power increase from running high octane but I’m guaranteed to run my best. Plus, I’m getting the best detergents with the higher octane. I have to admit, it does feel nutty filling up with 91 or 93 into a Yaris, but if that keeps my engine cleaner, so be it. In the old days, you would be limited by a set timing, but now ECU’s and variable timing have changed the game up and engines less likely to benefit from a higher octane fuel can now have some benefit.