“accelerating up a steep hill”

True! The modern electronic engine management pushes back the timing best under certain conditions: generally flat roads, generally even weather, and little-old-lady-from-Pasadena driving. Let’s say DC pretty much has the first two, for argument’s sake. As for the third. . .not.

@mikesol

“it will actually get worse mileage and therefore require more gas and run less efficient in dollars/distance compared to just giving it proper fuel.”

oh yeah: here.

Think of it like this:

Detonation and pre-ignition are instances where the gas combusts unevenly and/or too soon. This is caused by higher compression ratios.

Most cars don’t typically run at significantly high compression ratios.

Some do however.

So if anyone is really concerned about saving a few cents at a time over the life of their car, and of course prolonging the life of their vehicle, they should find out more about their particular car.

If your car has a turbocharger, you need higher octane. If your car is a high revving vehicle, you need high octane. And so on.

I’m skeptical about many of the cars though that I hear to be premium only. I drive a mid-90s Lexus LS400 that I absolutely love, it’s a bullet proof car, and I’m convinced that it’s the best car ever produced. However, the manual calls out for premium gas. I bought it used, and have always used premium because the previous owner was an elderly person that did everything the manual suggested. My own wisdom tells me to not to change anything on a used car such as this, but I’m not convinced that it ever needed premium to begin with. (And I know the arguments for it, but I’m still skeptical.)

Think about it – if the car retards its timing to defeat pre-detonation of the gasoline, it will then be putting out less power at any given RPM than it would otherwise. This will require you to push on the pedal harder to get up to speed, meaning you’re using more gas to get up to speed.

Find out what your car is built for and feed it the gas it asks for – no more, no less.

(Unless you drive a rotary engine, of course, in which case you feed it shitty gas when you’re feeling cheap and good gas when the prices are lower and always drive it like you stole it.)

“they are all completely incompatible

Forgive me, I think this statement is untrue. My comment seems in substantial agreement with gordon, micael, & billswift. Of the 12, I would say 30% of us largely agree, with some small differences in emphasis.

If Robin’s Miata doesn’t have modern features, he’s reducing engine life and resale value with ill-advised gas substitution.

Even if it does, I wonder if he may not in fact be saving money due to the safety compromise and lost hedonics, but I admit I don’t know how to correctly calculate these.

I don’t see how you get complete incompatibly out of this.

Love them humans.

“use premium gas”

This is such a big question it deserves deep consideration. Because cars are beautiful and important. I’m not at all an expert on cars – I don’t own one, don’t even drive! – but here is how I’d think about it.

First, I assume this is a newish Miata with a knock sensor, an electronic ignition and variable valve timing – modern electronic engine management. (If your car doesn’t have all this, then to use less-than-premium gas is penny-wise and pound-foolish, full stop.)

Second, that you own the car, you do not lease it. Third, that you are concerned with its resale value. Fourth, that you are concerned with reducing longer-term repair and maintenance costs.

As others have said, the issue is knock & ping. You may not necessarily hear “minor” knocking. Modern Miatas have all the groovy features above that would allow the car to run fairly safely – with little damage, since the electronics can dial back the timing.

This is probably why your owners’ manual may suggest premium instead of requiring it. However, as others here have noted, to use regular just robs the car of zip. So why have a Miata?

That aside, it could be argued that power and maneuverability are not just fun but are also important safety considerations if you are a good driver; they allow you to avoid accidents. So you are in essence compromising safety at the very moment you might need it for minor $$ savings in the gas price.

I don’t know how to calculate the rationality of such small gas savings in terms of the likelihood of the extra power saving you and the person with you in the face of a possible crash.

The use of midgrade with an additive to boost octane could be an ok compromise, I suppose, but again, you are still compromising car performance. And good performance is part of the hedonics (product quality, right?) of the car, which must have a calculable economic value in itself. But again, I’m not an expert here at all.

What seems irrational to me is to buy a gorgeous functional machine, pay strong $$$$ for its high performance, and then hobble it. But maybe that’s really just aesthetics.

My home state of Wisconsin mandates 10% ethanol in the regular and mid grade gasoline. Premium is still ethanol free.

Ethanol degrades mileage so badly that premium ends up being cheaper on a per mile basis.