Burning a bit of oil

[Crockett]

My son has noticed that his car is burning a bit of oil, mostly at start-up from being parked overnight.

It's quite high mileage (120,000) so I thought it would be a good idea to do a compression test on it to see what state the engine is in, it runs fine apart from this small problem. You know what they say - if you didn't want the answer you shouldn't have asked the question :)

The compression readings (in bar) were as follows (Dry/Wet/Variance)

1: 10.9/12.2/1.3
2: 10.8/11.4/0.6
3: 10.3/11.0/0.7
4: 10.4/11.1/0.7
5: 10.1/10.2/0.1
6: 11.4/11.8/0.4

My reading of this is that the engine is generally quite worn (as you'd expect for this mileage) with some more serious ring problems on cylinder 1 and some more serious valve problems on cylinder 5.

Would people concur with that analysis? Assuming a rebuild is needed how urgent might it be (I'm not sure in fact, how serious these variations are), bearing in mind that he maybe does about 5,00 miles per year?

Cheers
Daryl.

[Deleted User]

They don't look that bad to me.

My 2500s suffers from smoke on start up, I have put it down to worn valve guides.

I may be wrong but its not causing any other problems so I am leaving it for the time being.

Probably a head rebuild and some valve stem seals would sort it.

[Crockett]

That's what I'd thought (and hoped) too. Certainly I didn't think the compressions were all that bad. Believe me I've seen much worse. When 5 out of 6 have about 10 bar and one has 3, you know you've got a problem :)

Maybe it's something put onto the list of "at some point in the future"s?

He's mentioned maybe getting an unleaded head upgrade at some point, so that would solve the problem anyway, if it's valve guides. It seems most likely because it smokes much worse at startup.

I'll also ask him to take a look in the rear mirror at how much smoke it kicks out when decellerating from high speed. Certianly on the engine I mentioned above, there was enough smoke at that point to not be able to see cars behind properly.

On another (related) subject, what oil do most people use? We're using Duckhams Q 20/50 but I always felt that to be a little thin in the past and prefered Castrol GTX (when I could get it).

Thanks
Daryl.

[Deleted User]

I'm on unipart 20/50 for "older" cars.

Seems ok, not tried anything else so can't compare it really.