Did I hurt my Subaru with mid-grade gas?


#1

I have a 2004 Subaru Forester 2.5XT (Turbo). Subaru says it needs premium gas, and for the first 3-4 years, I stuck with that religiously. Then my mother heard on Car Talk one day that buying premium gas is a waste of money. Not being one to just accept someone else’s say-so, I came over to the Car Talk website and read everything I could find about gas. I came away convinced that if you put non-premium gas in your car and the car performs okay and there are no backfires, then you can use non-premium gas without worry. I did the test, and my car seemed to work just fine with mid-grade. In fact, I couldn’t tell any difference at all. So, I switched to mid-grade and have been using it for the past year or so.



Fast forward to last week. I was in a very minor fender-bender accident, and required some body work on my car’s front end. No structural damage was detected. After the collision repair was done, I drove home and things seemed okay. The next morning, however, my engine light was on, and I was hearing a funny whooshy/whiny noise from the engine (intermittent).



I took the car to the dealership, and they said my car had jumped time. They re-adjusted it. I drove home and everything seemed fine. Next morning, the engine light was on again.



Back at the dealership, they said my car had jumped time again. This go-round, they poked around a bit and found what they think is the cause of the problem: a clogged cam shaft solenoid valve. A replacement has to be ordered from Japan, because this part so rarely fails that it isn’t in stock here.



The guy at the dealership says my oil was really, really dirty. I have been very careful to change my oil every 5000 miles, and it had been 4000 miles since my last change.



Poking around with google queries, I started thinking I saw a connection between using lower grade gas, getting carbon buildup as a result, causing dirty oil, maybe clogging the solenoid valve. But it’s all conjecture on my part. Also, since this all cropped up only after the accident, it seems more like it was caused by some undetected damage.



So what’s the consensus? Is the problem my fault for using mid-grade gas, or was it simply a result of the accident? This has insurance ramifications, of course.



Thanks for any opinions, educated or otherwise.


#2

I don’t think mid-grade would have anything to do with carbon buildup. And if you are doing reasonable driving, 5000 miles should be fine (any 5 year old car’s oil will look ‘dirty’ at 4000 miles).


#3

It probably has a lot to do with your driving style, your car being a turbo. If you don’t normally “put your foot into it”, you’re not getting the full air charge from the turbocharger. And you’re not getting the potentially harmful detonation (“pinging”) from the increased compression resulting from the turbo’s charge of air, which will be evident with the lower grade of fuel.

If you’re not hearing pinging noises under typical load you’re probably okay. The grade of gasoline you’re using has zero effect on carbon buildup. Dirty oil: ditto texases.


#4

This board is full of Subaru engine horror stories. “Jumped timing”??? If they didn’t use a rubber timing belt about 20 feet long they wouldn’t “jump time”. If they are not blowing head gaskets they are suffering some cam drive problem.

If you are going to go 5000 miles between oil changes in a fragile turbocharged car, you better be using Mobil-1 synthetic or German Castrol, something that might keep “delicate” engines alive until the AWD light comes on…Then the “Game Ended” light comes on…


#5

Most turbocharged motors have a “knock” sensor that will make it OK to run plus or even regular in your car. You may have a decrease in performance which some people notice more than others. I don’t think you did any damage by downgrading your gas. In the owner’s manual somewhere it will state if Subaru “requires” or “recommends” premium gas. If it is required go back to premium. If is recommended you are not harming the motor.

As to the dirty oil. Your car is now 5 years old and you may notice the oil seems to look dirtier quicker now than when it was new. You can have an expensive service done to flush out the accumulated sludge and stuff that maybe dirting your oil. This is probably not necessary unless a visual inspection upon removal of a valve cover shows sludge building up. Since you have a turbocharged car it may need a higher quality oil and perhaps a shorter than 5,000 change interval. Turbocharged engines run a bit hotter and in particular the turbocharger itself gets hot and needs good lubrication to live a long time without replacement. A new turbocharger is pricey so you may consider more frequent oil changes. If it takes 12 months to go 5,000 then change the oil more frequently such as every 6 months regardless of miles driven.


#6

The oil change interval is the most likely cause. Five thousand miles may be fine if your driving is predominantly highway driving with few short hops.
If it’s the normal short hop, stop and go grind then 5k miles is too long to go between intervals.


#7

Subaru revised the oil change interval to use severe interval (4months/3750 miles) for all the 2.5L turbo engines. It is a requirement for 2008+ and suggested for previous engines. 5000 miles is not much. Note Subaru only specify’s using conventional and of course synthetic can also be used.

Lastly I remember looking at your Forester turbo as an alternate to my 2004 WRX. Premium is recommended not required. Check the inside of the fuel door for lanugage.


#8

Interestingly the enough the Subaru turbo engines are beyond stout and have turned out reliable. It is the standard base 4 cyl ones without turbo’s that have had blown head gaskets etc. The issue with Subaru on this board you see is headgaskets on the base 2.5L engine. Timing belts are a non-issue on the vehicle and simply get replaced every 8yrs/105k for $300-$500 which is much better than other vehicles.

The AWD systems are fine on manual transmission ones no electronics pure mechanical with same design since 1988 essentially. The automatic ones main issue is extra AWD sensitivity to tire wear differences(usually new different model tire placed into mix). The automatic’s has an expensive wear item in AWD called the clutch pack that runs about $700. Longevity is based on abuse it sees from owners typically.

You won’t see any AWD issues with Subaru listed on this board or elsewhere with manual tranny cars. Occasionally the rear diff oil gets neglected that is about it.

My extened family has 10 Subaru’s(non-turbo) with mileage from 60k-250k and not a single AWD problem(all manual). Somehow they escape the head gasket issues thus far.


#9

Thanks to all of you who have taken the trouble to reply. It is much appreciated. I’m glad to hear that the consensus is that the mid-grade gas was not the culprit (although the oil change interval is a suspect.)

Are there any votes for damage from the accident?

Also, for those of you who asked, Subaru does state that premium gas is required, not suggested.

Thanks again.


#10

Double check your fuel door language on recommended vs required. Maybe the salesperson was blowing smoke though but I recall him showing me it.

Fast compact SUV as I recall, a rocket.


#11

I think it’s much more likely that any problems that crop up immediately after an accident were caused by the accident.


#12

On Unibody cars, it doesn’t take much of an accident to deform the structure of the car. Look at the joint between the fenders and the hood ON BOTH SIDES of the car, damaged and undamaged. If they are both still the same, the hood fit equal on both sides, you should be OK, the damage confined to the fender. But if the gap has closed up on the damaged side, a little frame pulling will be required to make it “perfect” again.