Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

2015 Forester w/ manual transmission burns oil

Sorry if this is an old topic. My 2015 Forester burns oil, and has since we bought it. The dealer has been quite cooperative, and performed several “consumption tests,” eventually replacing the “small block.” The Subaru party line is that if you use the transmission to assist in braking you will burn oil. I have driven stick for well over 40 years with other makes of cars and never experienced any oil consumption. What gives? It is not like I am putting the car into 2nd gear at 70 mph or anything like that, just sequencing down through the gears as the car slows (I am also braking). The only thing I can figure is that this is the first car I’ve owned (I believe) that uses synthetic oil, and perhaps that is a new factor. Any suggestions would be appreciated!

This is a myth with a grain of truth. When engine braking, you get maximum vacuum in the cylinders, so weak (read: failed) rings or valve seals will pass more oil.

How much oil does it use (miles per quart)?

Have you tried not using the engine braking for double that number of miles to see if it affects the oil use?

If this were not a new engine I’d have said exactly the same as insightful.

However, seeing as it is a new vehicle, I have to wonder about the same questions texases did. With answers to these two questions we can help you a lot better.

Thanks, insightful, texases and the_same_mountainbik. The car seems to “consume” about 1 quart every 1500-2000 miles. I haven’t tried the not-using-the-engine-to-brake idea yet. That was Subaru’s recommendation, but old habits die hard! I am learning to do that now. I have found other posts about this issue via Google, but thought I’d ping the experts. Thanks again!

This is well known:

Pull quote:

Subaru has linked this issue to premature wear of the Oil Control Piston Rings. The fix is to replace these piston rings on affected models.

1 Like

@MarkT, as a fellow Forester owner (2016) I feel your pain. As you may or may not know, Subaru has recently settled a class action suit on this issue. Being a fan of the brand, I was disgusted by the way that owners reported they were treated and wrote this “Bite the hand” story covering the topic for CarTalk. Subaru vehicles have so many great features it breaks my heart that the company has struggled so long over this defect in manufacturing. I am a 4-time Subaru owner and I have had one short-block replacement. You can emerge from the end of this by working with Subaru, but if it happens to me again I am either trading mine to Subaru for a 2017 and an amazing deal, or I am driving it to Mazda, getting a CX-5 and never buying a Subaru again. FYI, the defect does not appear on manual vehicles only. Most of the Foresters built are CVT-equipped and they also burn oil. I doubt your engine braking is related in any way.

1 Like

Thanks gorhamj! I did get the new short block and warranty extension (plus a check for $13.83 for oil I had to buy while on the road to avoid engine destruction). Overall, aside from stonewalling, both Subaru and the dealer seem to be trying to make it right. But, jeez!, a new car burning oil from the get-go?!? It is more than a little disappointing to me. Otherwise, we love the car (although I wish the back hatch opened higher so I didn’t have to stoop to load things into the back).

1 Like

100k miles will use 80qts of oil? $320? Whew.

1 Like

Car buyers these days are very mpg sensitive, and so the manufactures are doing everything they can to increase those numbers for their cars. Not b/c the manufacturer cares about fuel economy so much, b/c they’ll be able to sell more cars with higher mpg ratings. And using thinner oil is one trick to boost an engine’s mpg. And this comes with an increase in oil usage. This isn’t just a Subie thing, all the manufacturers are pretty much forced to do it for competitive reasons. Not saying there isn’t something Subie specific about this particular problem, just the way the auto market is in general.

You know what I’d do in that situation? I’d just live with it. A quart every 1000 to 1500 miles isn’t much of a worry. Just monitor the oil level once a week and top off if low. Seems to me personal time not worrying about car problems is a much more valuable thing to conserve than a quart of oil every 1000 miles. Longer term, next time you buy a car you can do some research and buy one that doesn’t use so much oil. My early 90’s Corolla w/200K miles still uses 1 quart per 5,000 miles running on 10W-30 dinosaur oil.

Many (most?) cars using 0W-20 oil don’t burn a drop. But, reduce oil ring tension and/or change design to reduce friction even more…oops.

The bit about using the manual transmission as an assist in braking which then leads to excessive oil consumption is total BS.

Must be info from a service writer, service manager, or someone in Subaru of America’s “Tech Department”…

I’ve heard that theory, but never seen any proof yet. OP could do the experiment and post back, might be interesting to hear the OP’s observations on oil use w/engine braking vs without. I’ve always done the engine braking, double-clutching thing on my manual transmission cars and never had an oil use problem myself. But such a thing is theoretically possible I guess.

Like insightful said engine braking can increase oil consumption; so can high speed cruising.
It’s something that goes unnoticed if the overall consumption is low.
Suppose one has an engine that burns a qt per 20,000 miles if driven just right; and a qt per 15,000 miles when using engine braking and some high speed cruising.
This might go unnoticed with 5000 mile oil changes.
It’s a different story with an engine that burns a qt per 2,000 miles at best or 1,500 miles with engine braking / high speed.

1 Like

I’ve always thought that brakes are easier and cheaper to replace than a MT clutch, so I at a stop, I just popped it into neutral and used the brakes.

PS, I have a 15 Forester (CVT) and don’t burn any oil between changes. However, I did note a tendency of the dealer to overfill on oil changes, with the stated reason: so you will be protected if it burns some oil (or some such BS)

Valid point. I do that too sometimes, esp in low speed stop and go city driving. But the reason I prefer engine braking is I feel I have more control of the car, so engine braking imo is a safer way to brake. For example if I need to speed up for some reason to maneuver away from a collision, it’s in gear and ready to go. All I have to do is step on the gas. And if I need to stop very fast to avoid a collision, I have both the engine and brake system working the job, so I’ll stop a little quicker; and it seems like when that happens there’s less chance of the car fishtailing or brake steering when using engine braking in conjunction w/applying the brake pedal vs. just the brakes alone.

I use engine braking to a point. If I’m on a secondary road where the speed of traffic tends to vary up and down, I’ll often leave the tranny one gear lower and use the engine to make varying easier. I drive these types of road on every trip. I think it’s easier on the mechanicals than constantly shifting (or, with an AT, constantly accelerating and braking), and it’s certainly easier on my ankle. I’ve never in 45++ years worn out a tranny, and only ever had to replace one clutch… at 295,000 miles.

Yes, engine braking can increase oil consumption on an engine with valve stem seals that have some wear on them. As already mentioned, the cylinder vacuum spikes as the pistons try to pull air past a closed throttle plate. That can pull oil past the seals. But I’ve never had excessive consumption, so I don’t worry about it. At 338,000 miles my Toyota pickup still only used a quart about every 1200 miles. Of course I AM anal-retentive about keeping my oil plentiful and fresh, so I suppose that has been a factor.

My statement about stopping in neutral was intended to apply only for stops in city traffic. Slowing down at highway speeds I would downshift.

One point: engine braking, with modern brakes, will not improve the stopping distance, in my opinion. But I’m willing to be corrected…

Engine braking can become essential coming down a long hill, to prevent overheating brakes.
Once had to give my sister-in-law a crash (no pun intended) course while she drove in the mountains of Jamaica in a minivan loaded with people.
The brakes started to shudder and groan.

1 Like