Low octane fuel in a high-octane required vehicle?

I am proposing to get a new Subaru Forester. The Forester has 2 engine options, the usual one which works on normal/low octane gasoline, and the turbo which says that the high-octane gasoline is required… The turbo also gives less mileage… as a trade in for higher power… As I am new to a turbo engine, I was wondering what difference it would make if I use the low octane fuel in the turbo-engine… Will this harm the engine, or void its warranty ? The turbo already gets low mileage, and I dont think a fuel swap may make it a gas guzzling hummer anyways… (?) Are there any subaru-turbo owners here who use normal/low-ocatane gasoline in their vehicles… on a routine basis…

For everyday driving I dont mind getting a little lesser performance (mileage does matter, though), and I dont mind using the high-octane gasoline once in a while which I am touring on rough roads…



Turbo = premium.
Save $$ = non-turbo.

Yup, texases is correct.
If you want to be able to use regular-grade gas, then you should NOT buy a car with a turbocharged engine. Use of regular gas in a turbocharged engine will lead to damage that would not be covered by warranty.

You can’t afford to save money like that.

Ask to see what the owner’s manual says about premium fuel for the turbo motor and it sounds like you may have already done that. The key words to follow are “Must Use Premium” or “Premium Is Recommended”. You said “Required” from your source so that is your answer.

If you want to play you gotta pay. If paying an extra $3 a fillup runs afoul of your sensibilities, then opt for the standard N/A engine.

I know two extended family members, a father and son who each bought the turbo version of the Forester a year a part. They each enjoyed the extra power but would not get one again. Each traded the car within two and three years of ownership. This differs from many others I’ve know who normally kept their Subarus much longer. Another friend got the Outback with the six for the added power and loves it and said he will run it into the ground. In my opinion, it’s the better way to go if power is a big concern.

If performance is not a concern of yours, but low fuel expense is, then this is a no-brainer. The turbo engine is not even a viable choice for you. If you do buy a Forester with the turbo engine, running regular in it will result in lower performance, lower fuel economy (which will negate the $.20/gal price difference), and possibly severe engine damage.

My vote is for skipping the turbocharged version. The turbo comes in handy when you nail it hard, pull a steep grade at altitude, or decide to go drag racing but for a normal everyday driver you don’t need it.

In normal driving the turbocharger provides little or no boost so you’re essentially driving a non-turbo car anyway.

Pumping more forced air into a motor to extract more power is a short term fix for keeping engine size down but becomes a long term durability factor. Diesels in trucks where weight is not as much a factor are built to handle the higher loads, gas motors in Eco cars are not. A cheaper engineering response that is finding it’s way into other models as consumers are told they need these higher performance options. Another way to extract more money over time from the consumer with little gain other then an “ego” boost. Pass them by when ever offered.

Just buy a decal that claims you have a turbo, paste it on the back and get the best of both worlds; panache and economy with added longevity thrown in for good measure.

Turbo will give you more power, but most turbos also mean premium (high octane) fuel is going to be needed. Using regular when high octane is required can damage the engine.

The turbo also will REQUIRE more maintenance and that maintenance will be more difficult and expensive to perform… Fuel cost is a minor issue if you look at the over-all picture…

I was looking for a new car a few years ago and I tested both versions of the Forester(right after it got redesigned recently). You’ll want the turbo if you plan on driving on anything but flat roads; the normal 4 felt too sluggish for me when going up an on-ramp to the freeway.

As one person pointed out, the lower performance and mileage you’ll likely get will eat away at the extra $3 you’ll save per fillup. As for more maintenance, I haven’t had any more, or different, maintenance performed on my turbo CX7, than I had with my old car. More expensive, yes, I use full synthetic oil when it’s time to change it.

You wanna dance to the music you gotta pay the piper. Duh!

You can use low octane fuel in an emergency if you don’t open the throttle very much. There is a threshold of detonation that occurs at a certain manifold pressure. Keep the manifold pressure low and no damage.
I once limped into town using Coleman lantern fuel, which has an octane rating of nearly zero. As long as I didn’t try to go over 40 mph, the engine did fine. Open the throttle too much and the engine protested with that familiar can of marbles noise.
Ok, can of marbles is a poor analogy. Detonation actually sounds sort of like billiard balls colliding with each other.

“low octane fuel in a high-octane required vehicle ?”

Historically speaking, 92 is not exactly “high octane”…

Do you wear sneakers and a tee shirt with a tuxedo? Do you put ketchup on filet mignon? Then why buy a premium engine and feed it crap?

Since mileage is more important to you than performance, skip the turbo. Turbo chargers themselves are more prone to failure in the long haul because they spin at such high speeds (200,000 rpm) and are heated by the exhaust. These characteristics make them nor prone to long term problems and also are hard in the oil, whic is used to lube the bearings.

For long term reliability you’re better off without the turbo. And you’ll probably find that the turbo, in addition to requiring premium fuel, also requires synthetic oil…again an added expense.

You don’t need a turbo.

“Then why buy a premium engine and feed it crap?”

C’mon Whitey, 87 octane gas is not crap. It’s just not meant for higher compression vehicles. Talk like that could perpetuate the myth that high octane gas is inherently better than low octane gas. I don’t think you meant your comment that way, but others could read that into it.

Few engines can detect the difference between 87 and 92 octane…Because there is very little difference,It’s a cash-cow for the oil companies…

I suspect that the very first gallon of “ethyl high-test” was pumped into a car that did not need it…

If you run low octane in (most) motors that require high octane, your engine will “ping” which is an audible announcement that you’re startting to cause damage. Over time, it will just get worse.

Pay, or get the non-turbo version.