The manual refers to the fuel door sticker for the recommended fuel type (premium gas), but premium gas is now almost six dollars per gallon where I live. Is there a less expensive alternative that won't hurt the engine?

 

Lower octane gas than the minimum required 91 octane will eventually damage your engine. There is a reason why that sticker is on there. The engine is high compression and needs premium gas.

If the price of premium gas really is a problem for you, you can try the next lower octane gas and religiously add a bottle of an octane booster product at every fill-up. STP Octane Booster for example costs $3.97 in single qty from Amazon and you can probably get a deal from your local auto parts store if you buy it a case at a time.


It can treat 42 gallons, so you only need half a bottle per fill up. That works out to around an additional 10-11 cents per gallon based on the 18.5 gal tank (average will be a little higher because almost no one runs their tank to empty before filling up). The company claims a 2-5 point increase in octane, so you should not use it with any regular gas below 89 octane to be safe (mid-grade).

All that said, I would not use anything less than 91 octane simply because I have no way to test the truthfulness of the manufacturer claims. I do not have the budget to buy the expensive equipment required to do that, and even if I did the results are not exact, they usually measure to a +/- 1.5 octane point result. Your mileage will vary and I take no responsibility if your engine complains. If your engine starts knocking, go back to premium gas immediately.

 

Costco’s gas is Top Tier approved… and 91 octane typically the same price as others regular…

 

This is why I hate US fuel marketing so much. To this day so many still do not understand that for one thing, "premium" is not better in some way. Its really not. Its all about octane as flybd5 goes over - it is all about compression ratios. Even if you "think" it is not doing damage, it likely is. Especially on an older worn engine.

 

In fact, if your car is speced for regular octane, it may well get worse mileage with premium and might have less power.

Premium is not "better", but if your car is speced for that, you need it. Use regular if that's what your car is supposed to use.

 

My thoughts on this............I just use Shell premium, even the Ultra 94 seems to have a big dose of Ethanol (SAD!!) and after dealing with high output 2 strokes, I use Amsoil and Shell 91 if I have the option. If you want a hint to who sells the most consistent premium grades, look at where the motorcycle boys and girls fill up.

 

That would be my garage. I take out the ethanol on 5 gals of 93 with 5 cups water and a bit of red dye in a glass carboy, mix thoroughly, siphon the water/ethanol out the next day and use the pure gas on my BMW as well as my Honda EU6500is inverter generator. I can leave the fuel in the tank and not worry about the ethanol attracting water into the tank.

 

Fuel refiners don't market Premium as being a better fuel in general. That's mostly word of mouth and ignorant people assuming that's what premium fuel is. Yes, it is better if your car needs it, but it's a total waste of money if your car doesn't. The price of high octane gasoline is hardly a simple thing to explain. Car and Driver tried to give it a go in this article, but the fact is that the reason why higher octane = more money is complicated.

 

Lots of discussion... I wonder if anyone actually has read the "Top Tier" information. The two mentioned here (Shell, Costco) both qualify as Top Tier providers.
https://toptiergas.com/licensed-brands/
In both these cases, 91 Octane, 0 ethanol, and plenty of detergents are the ingredients to their "premium or signature" offering.

And incidentally, Ultra 94 also qualifies. I have no problem if some of my money is diverted to the local grain growers as opposed to... and my xkr thinks its yummy.

 

Ultra 94, in Canada, is sold only in select Petro-Canada gas stations. In Canada, it can contain up to 10% ethanol (which was a shock to me until I researched it). I can't speak for the USA but I know that Shell 91 (premium) is ethanol free in Canada. However, like all businesses and blend tankers, we are generally on the "honor system" so.....