Engine health and oil usage

[bobo83]

My MR2 burns oil at a fast yet consistent rate: I need to add around 1l every 400 miles. The oil gets dark quickly after an oil change as well.

I am no stranger to such cars, in fact, all my cars so far burned oil. My hatchback has been using the same amount of oil for the last 4 years and my previous MR2 was using 1l / 200 mi.

I'd like to address the root issue this time if possible.

To check the health of the engine, I performed a compression test a few days ago. The engine was at operating temperature and I did the test quickly, but forgot to press the accelerator pedal. Yet I still got pretty okay results:
You cannot view this attachment.

All cylinders were able to reach and exceed 180 PSI and the final results were within 10 PSI of each other. The gauge is a brand new Sealey one, and even if not fully accurate it does show consistent results across all cylinders.

There are no oil leaks, the rocker cover gasket and the PCV valve have been changed recently with Toyota parts.

In your opinion, what could be the cause of my problem ? Would a leak down test provide any more insight given the good compression that I have got ?

Thanks.

P.S. I have a heavy foot and I like to drive at high rpms.
 

[Ardent]

Is out of spec but relatively speaking not that much.

Owners manual deems 1L/1000km (621m) in spec

[Carolyn]

Max for a 1ZZ is 185 psi, so your compression readings are dandy.

However...  I can guarantee that the oil control rings are gummed up and stuck in their grooves.   The high readings after 10 revolutions are an indicator of wet compression rings.  It should not be possible to get above 185 psi in a healthy engine.

The only way to deal with this is do a light rebuild.  The pistons have to come out, be cleaned up and slightly modified, hone the cylinders and a new set of rings.  While the cylinder head is on the bench, it's a good time to give it new valve stem oil seals.  A few other new parts are good to do while doing the rebuild, such as a water pump, timing chain and thermostat.

This is easiest with the engine out of the car.  It's also a great time to give her a new clutch.

I've rebuilt quite a few of these...

No amount of flushes or potions will free those rings up.  I'm afraid a previous owner went too long between oil changes.

[bobo83]

Thanks Carolyn, I was afraid that an engine rebuild was the answer. I would be quite keen to do that myself but unfortunately don't have the space to do it.

In your experience, would such an engine last another few years if I top up the oil regularly ? I want to refresh my suspension but it wouldn't be worth it with a dying engine.

[Ardent]

I believe their are a few that do exactly that.

You are aware of it now, and have a reference point to know if it gets worse.

As C says, it won't get better on it's own  though.

[cptspaulding]

Thanks Carolyn, I was afraid that an engine rebuild was the answer. I would be quite keen to do that myself but unfortunately don't have the space to do it.

In your experience, would such an engine last another few years if I top up the oil regularly ? I want to refresh my suspension but it wouldn't be worth it with a dying engine.

Do you still have the stock manifold? If yes then the oil burning will more than likely be degrading the precats in the manifold. I've read of & seen pictures of a number of these where the precats break up & get shit further down the exhaust system causing partial blockages & power loss.

It's at least worth addressing that now, IMHO.

[Carolyn]

Do you still have the stock manifold? If yes then the oil burning will more than likely be degrading the precats in the manifold. I've read of & seen pictures of a number of these where the precats break up & get shit further down the exhaust system causing partial blockages & power loss.

It's at least worth addressing that now, IMHO.

I agree with the above observation. 

There's no reason why the engine won't last a good while and it might also get through emissions checks, but at that rate of oil burning it might struggle. 

Eventually carbon build-up in the cylinders will become a problem.

[bobo83]

I have recently installed a Toyosports manifold and the precats were in good shape, so at least that is some positive news.

I'll probably keep running the engine until I get to a point where I can swap or rebuild the engine. My other car has done 40k mi over 4 years and passed all its MOTs while burning the same amount of oil, so hopefully I'll be fine.

Thanks!

[Alex Knight]

An idea is to buy a second engine from somewhere like @J-SPEC (they are pretty inexpensive) and slowly rebuild that until you ready to swap them over.

[Carolyn]

I see you're in London, which isn't too far from us (Northants).

You could vist us on the weekends and use our facilities (and guidance) to do a rebuild.

[bobo83]

I see you're in London, which isn't too far from us (Northants).

You could vist us on the weekends and use our facilities (and guidance) to do a rebuild.

I would be really appreciative of such an opportunity!

[Ardent]

Grab with both hands.

An offer not to be missed.

[SurreyMR2]

I have seen various tests that have been carried out using Valvoline Restore & protect with good results. Unfortunately this is not available currently in UK, but as my 2 only has 58k on the clock and isn't burning a huge amount and zero smoke I think this is worth a try when it eventually released here.

This is one video I've seen, but there are others with similar results.

[Carolyn]

Oil burning 1ZZs usually don't blow smoke.  They burn the oil very efficiently.

[Beachbum957]

This has been out in the US long enough to get oil sample results. One confirmed result is the viscosity is low for a 5W-30 and actually some tests show it is in high 20 range at 100c after some miles, while new oil is in the low 30 range. The values for some of the wear additives typically used like ZDDP and other detergent chemicals are pretty average.

As for cleaning an engine, it would seem the anecdotal results are inconclusive.

People did report slightly improved fuel mileage compared to other 5w-30 oils, which would be expected for a thin oil.

[Carolyn]

With the last oil burner I had, prior to pulling it out and rebuidling it, I tried every possible method to un-gum the rings, just to see if anything worked.   This included some quite expensive additives and flushes.

Suffice to say, I ended up doing the rebuild.

Although, if oil consumption is not truly excessive, regular oil changes will prevent it getting worse.

[SurreyMR2]

Although, if oil consumption is not truly excessive, regular oil changes will prevent it getting worse.

This is good to know 👍🏻