Engine Oil

[bcmc33]

I currently have Miller?s Classic 20w/50 semi-synthetic oil in my car as recommended by Matty, and shall replace it with the same over the winter.

Both my normal road cars specify 5w/30 semi-synthetic oil ? as a matter of pure interest, what affect would it have if I put it in the Twink?

[Craig Elliott]

I'm not sure what the effect of the lower viscosity rating would be in terms of lubricating the engine - it might not be a good thing, you'd probably also get more oil passing down the valve stems. Given the normal incontinence of twincam engines I suspect that it would more or less certainly leak more..!

Craig

[leifanten]

thinner oil = more prone to leakage especially around the main seals and the valve stems, but also the wick effect through cork gaskets increases. The engines were built for single viscosity mineral oils, so all gaps and tolerances are for that purpose.

[JJDraper]

Surely not a 'straight' grade! 20/50 multigrade...

The original side valve motor may have used a single grade oil, but not a high revving Twinc.

I have tried 10/40 and it does leak, but so does 20/50! If you use the car in winter, it may be worth a change to 10/40 to save the cold start wear.

Me? I used Millers 20/50 sport in summer, standard Classic 20/50 in winter.

Jeremy

[frearther]

I'd be concerned about the ZDDP problem with modern oils. There are lots of threads on this - just search the archives for ZDDP.

Art

[bcmc33]

I'd be concerned about the ZDDP problem with modern oils. There are lots of threads on this - just search the archives for ZDDP.

I agree Art, that's why I shall stay with Miller's Classic oil which contains ZDDP.

[twincamman]

I tried synthetic in the super 7 tc and spun #3 main bearing ----I use 15 40 diesel sump oil now in all the lotus cars ----[2 tc and a Renault and the fv ] with complete success ---recommend it over normal oil now ----ed

[Lincoln62]

I read that modern engines have smaller oil galleries and different clearances as they are designed for thinner modern oils. Running these oils in an old engine could lead to problems. I'm sticking to the old 20/50 mineral oil.

Pete
66S2

[bcmc33]

I'm sticking to the old 20/50 mineral oil.

I thought the best informed advice was 20/50 semi-synthetic.

[pereirac]

Years ago it wa recommended that I use Mobile 1 (there was only one version then) and I have stuck to that. Engine has done about 50k since then and apart from a lower oil pressure (35psi) I have not had any issues..apart from the drips o il on the garage floor and the underneath of the car, but it keeps my chassis rust free

Carl

[bcmc33]

I have not had any issues..apart from the drips oil on the garage floor and the underneath of the car, but it keeps my chassis rust freel

My engine comes out tomorrow for a gearbox change, and while it is out I plan to do the Rohan Hodges sump mod and make an attempt at curing the the film of oil that persists around the sump gasket.
But a question comes to mind - with complete sealing of the top and bottom of the cork gasket, will not oil eventually bleed across and still result in a film on the outside?

[bast0n]

I use Millers 10/60. No increase in leaks, better pressure when very hot after long Alpine blasts. Recommended by Pat Thomas - good man of his parish. Full of sound common sense in all things Lotus.