Excessive oil consumption?

[ocheye]

When I picked up my 'new' Stag I checked the oil level before driving the 130 miles home but in my excitement I actually checked the auto box level. The vendor said it didn't use oil but added the rider that he hadn't used it a great deal which was borne out by the MOT's. It ran well and sounded great but when I checked the correct dipstick (yes, I know, there were 3 dipsticks in this story!) the oil appeared to be very low.

I topped it up and haven't done a huge mileage since but this weekend did a couple of hundred miles and I appear to be getting approx. 100 miles per litre.

There is some pale blueish smoke from the nearside exhaust and I can get a few microspots on my hand. Haven't noticed anything looking in the mirror through the rear hood window but the perspex gives a pale blue tinge anyway.

I'm fearful that I may need an engine rebuild though it does appear to run really nicely but I've no other Stag nearby to compare it with. I'm going to get a compression check done (I believe I should get it done both wet and dry) and see what that throws up. Sadly, I've used most of my budget buying the car so it's going to be a DIY affair I think.

I had thought that a bit of oil is a lot less expensive than a rebuild but it may not get through an MOT emissions test.

Any pointers? My thoughts are rings or guides

Andy

[Escape]

Do you know what oil is in the engine now? Sometimes older cars suffer from excessive oil consumption when a modern 'light' oil like 5W30 is used. Using a more suitable 20W50 can cure it for little or no cost at all.
An easy and cheap way to check for major compression loss is to put your hand over the oil filler hole with the engine running. If there is blow-by at the piston rings, you will feel some pressure. If the oil comes from the valve seals, the blue smoke in the exhaust will probably be most noticeable at start up after the car has been sitting for a while.

Filip

[ocheye]

Do you know what oil is in the engine now? Sometimes older cars suffer from excessive oil consumption when a modern 'light' oil like 5W30 is used. Using a more suitable 20W50 can cure it for little or no cost at all.
An easy and cheap way to check for major compression loss is to put your hand over the oil filler hole with the engine running. If there is blow-by at the piston rings, you will feel some pressure. If the oil comes from the valve seals, the blue smoke in the exhaust will probably be most noticeable at start up after the car has been sitting for a while.

Filip

Thanks for that advice Filip. Sad to report that I'm using 20/50. I tried the oil filler hole trick. There was a significant drop in revs when the cap was removed and an increase when I put my hand over the filler. Don't know if it was my imagination but it seemed to create a slight vacuum (it appeared to suck slightly) I certainly wasn't aware of any pressure on my hand. Is that a good sign?

[V Mad]

There was a significant drop in revs when the cap was removed and an increase when I put my hand over the filler. Don't know if it was my imagination but it seemed to create a slight vacuum (it appeared to suck slightly) I certainly wasn't aware of any pressure on my hand. Is that a good sign?

The vacuum at the oil filler is normal. This is generated by the breather system; cam cover to carburettors. The idle speed response is due to the extra 'air' weakening the mixture.

It is possible in theory to burn more oil if oil is getting out of the cam cover into the breather system. Whether that could be significant though I couln't say.

[ocheye]

The vacuum at the oil filler is normal. This is generated by the breather system; cam cover to carburettors. The idle speed response is due to the extra 'air' weakening the mixture.

It is possible in theory to burn more oil if oil is getting out of the cam cover into the breather system. Whether that could be significant though I couln't say.

Hi Chris
I thought it seems normal. Does that mean I can rule out rings? And maybe guides?
Andy

[V Mad]

No Andy, dont rule out anything until you have done the usual checks, most of which are well known (compressions with/without oil through the plug holes etc.) .

All I was saying is that if all the usual suspects look unlikely, consider the breather as a possibility.

[ocheye]

Hi Chris
Can't check compressions for a couple of days but is there any suggested check/fix on the breather side of things?
A

[V Mad]

Well, if you take off the cam cover breather pipe, is it quite oily inside? The pipe splits into two pipes then into the carbs; have a look at the carb end of the pipes. If a lot of oil is getting up there, that may suggest its something to look into further.

One test that I have done is to put the end of the breather tube from the cam cover into a tin can. Take it for a 10 mile run and see if there is any oil in there. (but block off the carb breather inlets otherwise the mixture will be upset).

[Guest]

This might be over simple, but have you checked for oil leaks?

Obviously easy to spot when the cars been standing for a little while from the puddle on the ground, but also worth getting under it and seeing if the underside is covered in oil if the leak is worse in motion.

[ocheye]

This might be over simple, but have you checked for oil leaks?

Obviously easy to spot when the cars been standing for a little while from the puddle on the ground, but also worth getting under it and seeing if the underside is covered in oil if the leak is worse in motion.

Haven't found any leaks of note!

[ocheye]

Well, if you take off the cam cover breather pipe, is it quite oily inside? The pipe splits into two pipes then into the carbs; have a look at the carb end of the pipes. If a lot of oil is getting up there, that may suggest its something to look into further.

One test that I have done is to put the end of the breather tube from the cam cover into a tin can. Take it for a 10 mile run and see if there is any oil in there. (but block off the carb breather inlets otherwise the mixture will be upset).

No sign of much getting into the pipes. Fairly dry really. Do you think this might point to the filter being clogged and if so could that cause my problem? My instincts say not but I'm not used to this type of engine. My last 'classic' had a similar problem but it resulted in back pressure and oil came through the cap and the dipstick tube etc. A replacement PCV completely resolved that problem

[GDPR]

Use the car, put decent oil in as required, should find the problem improves as you put some miles on it...

100 miles a litre usually equals a significant, very hard to miss, amount of smoke out the back..

[ocheye]

Use the car, put decent oil in as required, should find the problem improves as you put some miles on it...

100 miles a litre usually equals a significant, very hard to miss, amount of smoke out the back..

Well, I've just about done a rolling oil change since I bought the car. I've done around 500 miles but mainly in wet and windy conditions meaning the hood was up so it wasn't easy to see any smoke on the move. It's also an auto so less easy to induce overrun. Idling on my drive, the nearside exhaust pipe emits pale blue exhaust while the other is almost invisible. Putting my hand in the exhaust smoke reveals small oily spots as I've said. To my mind that implies a problem on one bank only. I'm using Halfords classic oil which is a basic 20/50. It was the only place open for 20/50 on a sunday and I didn't want to put in a thin or semi synthetic oil. Don't know if it is a 'decent' oil or not but it was actually their cheapest oil (and their only 20/50) in stock. I'd love you to be right though Kryten!

[GDPR]

Order some Valvoline VR1 20/50 from Eurocarparts - would personally only put Halfords 20/50 on a bonfire to keep it going...

[kgnich]

I'd also suggest waiting before diving into an engine rebuild. Piston rings in rarely used cars tend to stick ( they did on my e type causing the sort of symptoms you are experiencing) and with use they can reduce oil consumption. That's my experience on a couple of classics I have had... Would be great if this solved your " problem"! Best of luck and let us know how you get on.
Graham