The Lotus Grand Tourers

Did someone ever put seals on valve stems to reduce oil consumption ?

I think some have, but why would you need to? The valves are designed to have a small amount of oil go down them to help reduce the wear between the two surfaces. I don't get noticeable oil consumption, so I could only imagine that your guides would be warn if yours is using a lot of oil and you've eliminated the other suspect areas.

912 engine tolerances are pretty slack compared to moderns so you need to use the right oil grade to keep oil consumption down.

Try Castrol 10/60 synthetic oil and your oil consumption may fall. Mine uses very little oill on 10/60 but there was significantly more consumption on Mobil1 15/50.

For this reason it will drink like a fish on a 40 grade oil but I guess you knew this already.

AndyC wrote:I think some have, but why would you need to? The valves are designed to have a small amount of oil go down them to help reduce the wear between the two surfaces. I don't get noticeable oil consumption, so I could only imagine that your guides would be warn if yours is using a lot of oil and you've eliminated the other suspect areas.

I put a new head gasket 2 weeks ago and will be please to use less oil without stripping it another time . I can't understand why it doesn't burn oil before and now it do (yes I know 5 minutes before dying he was alive )

Lotus-e-Clan wrote:912 engine tolerances are pretty slack compared to moderns so you need to use the right oil grade to keep oil consumption down.

Try Castrol 10/60 synthetic oil and your oil consumption may fall. Mine uses very little oill on 10/60 but there was significantly more consumption on Mobil1 15/50.

For this reason it will drink like a fish on a 40 grade oil but I guess you knew this already.

Temperature is very hot in France at the moment and my engine start to drink too much oil. I put 10W60 2 days ago and will follow that. Check that this morning and seem to burn nothing with a lower temp outside but I did on 50 miles.
Do you think temp can play a significant role ?

Yes, obviously if the oil is running TOO hot (100 - 150C) it will be dramatically thinner than spec and a significant amount of oil will be lost past the piston rings (as well as the guides if worn).

From my experience of monitoring sump-oil temp and cooler-oil temp simultaneously, the oil temperature increase is most significant at revs above 4 krpm and the position of the Excel oil cooler in vented radiator air will be adversely affected by high ambient air temperatures.

I run a Laminova water-oil cooler (heat exchanger) on my high revving Clan and this is the best way of ensuring the oil temperature equilibrates to water temperature (82C) most of the time and sump oil temperatures don't get hotter than 95C, even when wragged.

If I loved my Excel as much as my Clan and had an unlimited budget I'd fit an Laminova to the Excel too.

Forgot to mention that compression test are very good (near 13 bar on each) that's why I was suspecting valve guides.