gerry100

We're thinking of upgrading our DD to a fun sports sedan
(Separate post about that

Many of our choices note premium fuel.

I assume this is to bump up max hp/torque numbers and that the cars will run fine on RUG

Am I right?

Kenny_Stang

To maximize fuel efficiency (as well as power) most mfg's have bumped up compression and to keep cars from knocking, they require premium fuel to get the most out of the engine. That being said, all engines will detect knock and pull timing, so you can run lower octane fuels without causing too much damage, but efficiency and power will be sacrificed, and I would also have concerns of the longevity of an engine that was run with a lower grade of fuel.

Marioshi

Yes, the car should run fine on regular gas, having said that, I would put the gas it calls for, the savings isn't great enough for the car to run less than ideally. If you are looking at sports sedans, you should be ready to pay for premium IMO.

Chris Stack

FWIW, when my TSX was new, I ran a tank of 87 and a tank of 93 back to back; got about 2mpg less on the 87. That means the price is basically a wash. (400 miles at 25mpg and $4 gas is $64; 400 miles at 23mpg and $3.60 gas is $63).

DaGou

What Kenny said, if the OEM tells you to put premium in it, put premium in it. What you going to spend $40K plus on sports sedan and void the engine warranty saving a few dollars on cheap gas?

The car was tuned for premium. You want the car to knock when you step on it and run like 3 legged dog?

While I am on a rampage I really hate it when people go the other way, putting in premium when it calls for regular, thinking the car will run better or have more power. Not true, engines run best when they use the fuel the car was designed for. Premium fuel does not run as hot or burn as good as regular. You will actually lose power running premium if the car was tuned for regular. Same holds true for putting race gas in car tuned for premium. It robs you of power. Goggle it! What it does do for you is helps prevent knock by limiting PRE-IGNITION when the engine is extra hot in race conditions.

CMK

It's a legit question. If premium's recommended, it's for performance and economy purposes. Like Chris said, monetary savings end up being a wash, and with 91 (or 93) you get the "top of the line" additives and detergents.

vader1

I had a Subaru turbo back in 2007 that ran like crap for a while. The dealer could not figure out why it would buck and stutter under boost. I was always using premium. The end result of fixing it which included reflashing the ECU, or at least the techs theory was, the dealer filled it up with regular and when it was transferred from one dealer to the one I bought it from, the kid who shuttled the car beat the snot out of it. (It arrived from a 30 miles drive with a 15mpg readout for that tank)

If the theory was correct, and Subaru uses a "learning" ecu, the kid beat the snot out of it running the crappy gas and the computer detected knock and pulled timing aggressively to protect the engine. The ecu "learned" these spots where knock was occurring and adjusted the map to avoid detonation. These new bits of bad data remained even after I had been good to the car and ran premium gas.

I don't know if that is how Subaru ECU's function or not, but that was the story they gave me and it sounded good and the car was back to normal. But it took a few trips to the dealer to get it sorted out.

I always get the recommended fuel.

rob-2

Honda 11.2:1 ran 87 oc for nearly 100k. No issues

mosesbotbol

On our Volvo, they recommend regular, not premium FWIW.

FearlessFife

This thread reminds me of my 2005 Civic I drove for right at 4 years. About 3 years in I accidentally put in 91 octane and it was a completely different car going forward. Quieter, smoother, more enjoyable. All three cars at our house require premium, and I am totally fine with that.

Premium FTW.