My daughter bought a 2007 S a couple of months ago. We changed the oil at that time, and 2,000 miles later it has gone through over 2 quarts. While I know these engines can burn a lot, I just want to be sure there's nothing else going on.
Here are key points / observations:
- car has 113K on the clock
- running 5W30 oil
- valve cover replaced in 2018, looks like it was genuine Mini
- turbo replaced in 2016, cannot detect any axial play in impeller
- no significant external oil leaks, spark plug cavities are clean
- inside of tailpipes has a lot of dry black soot
- exhaust is not noticeably smoky, however
- small amount of oil in the hose from valve cover to turbo (and therefore also some on the pressure side of turbo - to intercooler)
- absolutely no oil in the intake hose after intercooler (top of compartment, passenger side)
- definitely some oil in the small hose out of the passenger rear of valve cover (to intake)
- oil cap can be pretty easily removed with engine running (there is vacuum but it isn't overwhelming)

So I am looking for input. How do I tell if the PCV in the valve cover is doing its job? If that isn't it, then I assume my next stop would be compression testing.
She's on a limited budget, so I'm trying to help her as much as I can.

Grateful for your suggestions...

 

Two qts in 2K miles isn't bad. Many only get 500 miles out of a qt. Main reasons for these otherwise good engines to burn oil is a single piece oil ring (instead of a three piece), and worn out valve stem seals. Neither of which is economically easy to fix. If compression on all four is within 10 - 15% of each other, your cylinders are probably OK. Typical readings are 140 - 160 PSI, but cheap equipment can cause lower readings. My Harbor Freight gauge indicates about 110 on all four (hose ID is excessively large and there's a lot of it) but a pro's gauge reads around 160 --- this on a rebuilt engine.

Crankcase vacuum at idle indicates part of the PCV is functioning correctly. Oil in the PCV hoses is also normal, more so for the rear hose. Turbo PCV hose should have a minimum amount of oil. It's only active during boost conditions, so driving habits dictate PCV function. That's the purpose of Oil Catch Cans, to trap PCV "waste". Next time "you're in there", maybe pull the intake manifold and inspect valves for crud build-up --- PCV waste that sticks to the valves. A walnut blast is the typical fix and will significantly improve performance. There are kits available for the DIY'r.

Turbo should have ZERO play, neither axial or radial. Only smooth and easy rotation. If any play exists, that's a possible source of the oily turbo. Maybe clean both hose and turbo chamber then drive it gently (no boosting) for awhile to see where oil comes from --- valve cover or turbo. Turbo will always spin, therefore possibly leak, while turbo-side PCV will only activate during boost.

Best of luck and keep us posted ---

 

Thanks very much - this is really helpful info! We are going to be closely monitoring consumption over the next week or so - I want to see whether it is 2 quarts over 2K miles, or whether it has been accelerating more recently.
While I have a pretty decent, ever-growing tool collection I don't yet have a compression tester. Will either buy one or have my mechanic do a compression test for us. I figure it won't hurt to know where things stand.
Fingers crossed that it it isn't rings or valve stems - but who knows?

 

For starters I'd quit using such a light oil. 10W-30, forget about it. Go to 10W-40. ExxonMobil makes a high mileage 10W-40 in synthetic. This will cut your oil consumption in half. Mini recommends 10W-20 on new engines. But they don't address the engine issues, so don't dare tell you heavier oil will help with this engine's issue.

 

Thanks for this reminder! I was intending to look into what viscosity ranges are acceptable and take it up a notch or two...

 

Zero play is absolutely NOT true for a stock BW K03 turbo with a plain bearing (or any turbo with a plain bearing).

I can't recall the spec for axial play (less than 0.004" is a best guess).

TIR, at the outer end of the compressor nose is on the order of 0.018". IIRC, you might find the specs in a previous posting.

Zero play with a plain bearing design means there is insufficient fluid to provide the damping required to stabilize the rotating mass. Bad things will happen in the case of no play.

 

Strongly suggest you do not use a 10W anything oil, unless you can find one that meets at least the LL-01 spec, or better still, the MB 229.5 (a bit more stringent than BMW's LL-01).

There are any number of 0w40/5w40 oils that meet ACEA specs for a turbo engine and are readily available.

 

It is time to be really hard nosed about the financial wisdom of investing in a high miles 2007. I have considerable experience with one that I'm really glad to be rid of.

The anecdotal evidence is that the early N14 are dreadful oil guzzlers - mine certainly was. I never did figure out root cause, but I suspect it was very likely bad valve stem seals.

I'm really skeptical of the value of doing a compression check without also doing a leak-down check as well. I would be really concerned if the valves are showing signs of leaking as well as high oil consumption. A compression check by it self won't provide a complete picture of cylinder health.

 

Asking is ExxonMobil oil meets BMW specs is absurd. The bottom line is his engine is burning oil. Raising the viscosity tob10-40 will GREATLY improve the performance and dependability of his engine. Whatever is left of its life, that is. If he runs anything zero weight he WILL CERTAINLY ruin his engine sooner. You need to get your head out of the BMW clouds (thinking that following their guidelines is the only answer) and address the facts, which is something BMW mini will never do because they won't admit failure on design. So, why don't we help others with their engines so they can run them to failure over months of service instead of weeks. Burning a qt every 1K miles is bad for pocket book, engine, cat converter and PLANET!

 

Thanks for your concerns regarding the placement (and I suppose the condition) of my head. I'm as certain as I can be, however, that I'm quite firmly grounded in objective reality.

I'm not so sure you've made a solid case for using a relatively heavy oil in an engine not designed for it.

It is also not at all clear that a 10w40 will result in a significant reduction of consumption. At temp the 10w40 is only about 20% thicker vs. the 5w40 (based on typical viscosity specs). During warmup the 10w40 is closer to 150% of the 5w40's viscosity.

There are other factors to consider, besides viscosity, since the N14 is not a simple 1980s era V8.

If it were mine, I would use a 5w40 and put up with the high consumption in favor of giving the other elements of the engine the oil they were designed for.

Given the very high cost of rebuilding the head or engine, I would also opt to spend a relatively small amount on oil and drive it as is.

 

Let's put into perspective what viscosity is: water is around 1 at 20 C. You are running an oil that is less than or probably equal to water. Yes sir, use away, because your engine is not designed for it.

 

From my experience of rebuilding an N12 the biggest culprit for the excessive oil consumption seen with the Prince engine is the factory fitted 'one-piece' oil control ring fitted to each piston. Before the rebuild my partner's N12 was sucking 1 litre of oil out of the sump very 800 miles. After replacing the factory fitted oil control rings with '3-piece' oil control rings, oil consumption went to zero. Now I did replace the valve guide seals previously and didn't really see a whole lot of improvement. Therefore, the conclusion I have come to is that you have to get the head off, sump off, piston assemblies out and replace stock rings with a better set.

 

What did you do for bore refinishing?

How many miles? Much bore wear?

 

Wasn't too sophisticated with the decision on what to do with the bores, basically deglazed with a bore honing tool, fairly low cost solution from an Amazon vendor. Have heard people suggest using a course Scotch pad. You just need to deglaze so the new rings can bed in. Used a single grade mineral oil with running in additives for the first 1,000 miles after which I switched to a 0/30W synthetic. Car went back on the road 1st Aug 21 with 125,000 miles and is now approaching 130,000 miles. Nearly five months and 5,000 miles and hasn't drunk a drop of oil.

As for bore ware, felt the slightest lip at the top of each bore but not enough, I felt it didn't warrant rebore or new liners. Before the engine issue that caused me to take the car off the road,I had the engine compression checked and leak down tested by two Indi's - both came back with very positive feedback on cylinder condition - 200 psi per cylinder and now noticeable leaks. Problem I had was a faulty inlet valve seat which would come loose as the engine came up to temperature (hot idle misfire). Valve seat eventually dropped out. Had to replace all pistons and repair the head.

 

This is an informative & interesting discussion... We have decided to take her car to a local independent who has extensive Mini experience (they were the first and main dealer-alternative in our area when the new Mini came out). Going to have them do a leakdown test and also give a general once-over on the engine, as we are still trying to figure out whether certain noises are normal, or signs of worn components. Should be out the door for under $200. In this situation I feel it is worth paying for some knowledge, and then we can decide our course with some confidence.

There is a small part of me that would consider taking on the head / rings myself if they prove to be the issue, however I know it will be a huge time suck (both the researching and the actual doing) and all of this on someone else's daily driver. Most of me doesn't want that stress...though it would save a lot of cash. The aforementioned Mini shop is so busy they have had to stop taking on engines & heads lately, but even if they were, I have a feeling paying for a shop to rebuild the engine just wouldn't make financial sense (guessing it would cost what the car is worth). I do think @Mickey Mini 's idea of doing an "in-frame" rebuild is interesting... It begs the question of how thoroughly does one go thru things to get a good result - looks like the "middle road approach" paid off for you!

We will definitely try the 5W40 oil, and I also have had a recommendation for Lucas oil stabilizer which may reduce the burning. Not usually a fan of additives, but may be worth a try.

 

Update: We had the car evaluated by a good local Mini specialist. In a nutshell, compression/leakdown did not show significant issues. They feel that the oil control rings are likely a large factor in the oil consumption. They said we might also try changing the valve cover, though that likely would not cure the problem (they recommended only OEM as the cheaper knockoffs seem to be unreliable). We have not done that yet. They also investigated an odd noise we'd been hearing. Turns out the oil pump had ingested parts of the timing chain guides (which had previously been replaced by prior owner. So we replaced the oil pump.

Unfortunately the oil consumption has been increasing - now getting 600-800 miles to a quart it seems. I think we're either going to have to look into a rebuild or just sell the car. It is too bad, cause it is in really good shape otherwise. I will see if I can find anyone locally to talk to about a rebuild, but am doubtful. The specialist (above) is great, but they don't get into rebuilds - their shop is too busy with other work.

If I had more free time, I'd consider tackling it myself, but looking at the big picture I just don't think that's smart.

If anyone has thoughts, I'm all ears (well, eyes in this case)...

 

It's going to come down to how long you want to keep the mini as to the next step. You certainly need invasive work to fix that engine, another option is to have an engine swap, simpler for a garage to undertake and would come with a warranty. Doesn't have to be a new engine, could consider a refreshed unit from an engine builder. My partner's mini has clocked 8,000 miles since the rebuild and has gone from a litre of oil every 800 miles to 0.3 litre in the last 8k.

 

Yep, you're spot on. I checked with one good local shop today - they've done Mini engine replacements before and said they would have to check current pricing but ballpark $5,000 - $8,000. I guess they source their rebuilt engines thru Mini. But the rest of the car will still be the same age & miles, of course - which leaves opportunity for future "investment". And, the other concern is you really have to trust the shop - I've read too many horror stories about engine replacements where things were done sloppily or halfway.

Still considering the angles but it may be time to cut our losses.

 

I’ve read that valve stem seals on these older N14 engines can start to get hard and cause excessive oil consumption… A couple members here have done seal replacements without removing the head. If your handy in the garage, might be worth a weekend of tinkering?