Engine oil

The original Lotus Service notes recommends 3.5 litres including filter change of 10W/30 SF or SG, 15W/40 SF or SG, Mobil One 5W/50 SG

If it were a new car the oil choice would be straight forward, just follow the manufacturer’s recommendation. Unfortunately the Lotus recommendation is 17 years old and oil has moved on a bit.

What the numbers mean…

The numbers show the relationship between modern multi grade oils and the SAE single grades.

While your lawnmower engine, being small, slow running, and used mainly when it’s warm, will run happily on SAE 30, a car engine needs something thin enough to pump instantly to the camshaft when cold, but thick enough to maintain the pressure when hot.

10W 40 means its starts from cold with the same flowing characteristics as a SAE 10 single grade oil, but rather than thinning as the temperature rises as an SAE 10 would, it thins no more than a SAE 40. Similarly a 5W 50 starts off as a 5 when the ambient temperature is -18°C and doesn’t thin anymore than a SAE 50 by the time the oil is boiling.

You might wonder why you would ever need a 0W, it’s the same as a 5W with an extra bit of something that keeps it pourable under even worse conditions.

We used to consider Duckham’s 20W 50 as being a thick oil and now we have fully synthetic 10W 60 being recommended. Fortunately the synthetic oils flow better generally, so the comparison is not exact.

In the middle of the UK 10W-40 would be a good choice. 5W-30 would be more appropriate for Norway and 15W-50 for North Africa. Then there are track days…

Some of the things said on the subject of engine oil.

Castrol say:

Changing the oil every 6 months Magnatec 10W-40 SS would do a good job. Doing any track days, EDGE 10W-60 FS would offer better performance and protection.

For the extra cost they recommend EDGE 10W-60 FS anyway, but do the oil change once a year for low mileage cars, as it will easily do the mileage.

They also recommend EDGE Turbo Diesel 5W-40 and EDGE 5W-30

On the subject of high mileage engines

See also here http://lotuselancentral.com/forum/viewtopic.php...28&highlight=

Here’s what they had to say.

If the engine was very dirty, and had not had regular oil changes, and the engine has a bit of wear - then it is possible where there could be some carbon deposits built up around the valve guide seals and piston rings where this carbon is actually providing a final seal - if an engine oil with good detergent properties is used, then over time it can clean away the deposits and you could get some extra usage - but you wouldn't see this straight away. A more likely scenario could be that the oil is oxidised so it is thicker - when you change the oil, the new oil will be thinner and would also show up any wear - especially is it a synthetic which tend to be thinner than the equivalent mineral oils. If in doubt then a semi synthetic would probably be better bet - detergents in oil don't necessarily "clean" the engine, but stop dirt sticking to it, and hold it in the oil so when it's changed the dirt is flushed away.

From this you could assume for high mileage engines that have always been running on semi synthetic oil it may be best to stick with it.

ESM says:

Fully synthetic oils are the best by some distance. Friction losses in engines drops by around 4% with a synthetic oil - this gives more power and more economy. They also are the most effective at limiting wear - which is why many engines are best run in with a non-synthetic.

Some older engines (I mean older, I don't mean late 80s) need a more viscous oil because the bearing clearances are larger. Chris Foulds doesn't like synthetics too much largely because of this.

Different oils swell/shrink seals differently. So if you have a borderline seal. One oil may be worse than another for loss through that seal. Which oil minimises your loss may vary depending on which seal causes the leak because all seals aren't all of the same composition. Oil formulation is scarily basic when it comes to seal compatibility; they are formulated with a mixture of elements known to cause either seal shrinkage or swell which are balanced to break even(ish). So worse oil loss isn't necessarily a synthetic vs semi or non-synthetic oil issue more a formulation to formulation issue (if Mobil 1 gives you issues another synthetic 0W40 oil might be better).

Synthetic oils can achieve low cold viscosities. So HVLs will pressurise faster with them, although any drips from leaky seals will be worse for the same reason. I'd certainly go 0W for choice. I prefer a W40 because it will give greater engine protection than a W30 (as a result of its higher viscosity) and the last approval Lotus issued was for a 0W40 not a 0W30. That's not to say a W30 won't be ok and it will incur less in the way of viscous losses but I'd say the Elan's engine is from the W40 oil technology era and so I stick with that because clearances etc are likely to have been designed with that level of viscosity in mind.

Engines run with synthetic oils are cleaner, if you put synthetic oil in an engine previously run on non-synthetic you can dislodge a lot of gunge so run a short first oil/filter change interval if you switch.

Amsoil says:

To use any 60 grade oil in these engines is crazy. This is the thickest grade of engine oil there is. Whilst we sell a 60 grade its confined to pre war Harley Davidsons and nitro drag cars whose superchargers force the fuel past the rings (if they have them) and into the oil therby diluting it; so they start thick to end up with something that will let the engine survive. If you are tracking your car and the temperatures are so high that the use of a 60 grade oil means that its effectively a 30 or 40 at these temperatures then please ask yourselves about the efficiency of the rad or oil coolers (if fitted) Bottom line is get the temperatures down and use the correct grade. The engine oil is meant to be an indespensible part of the engines system rather than being used as a prop. The problem with thick oil is that it causes more friction / pumping losses which in itself creats extra heat , robs power and efficiency and can actually lead to oil starvation when an oil pump cavitates. Edge is a good product but please stick to what the manufactures originally specified. The improvements in oil which mainly refer to the appearance of full synthetics, have resulted in very much stonger and longerlasting products. Amsoils products are at least 3-5 times the film strength of mineral oils and this strength allows the use of thinner oils to advantage. Not too sure how a synthetic oil can be thinner than a mineral oil? If it where it would just be graded differently so that it would be the same , if that makes sense.

What LEC members are using…

Gareth: Changed from 10W/30 to 10W/40

Paul: Duckhams 10W/40 to Castrol Edge Sport 0W/40 found a slight leak, going back to 10W-40

Muley, Jim: I’ve Been using Mobil 0W/40 but switched to the Castrol Edge 0W/40 as the car had nearly 70,000 miles I'm thinking of trying a 10W/40 SS

Paul P: Castrol RS 0W/60 FS 110,000miles

Simon P: Put 0W FS in - Made the valve lifters noisy so switched back to 10W its quiet again (10W?)

Kmckmc: Shell 5W/40 - Castrol FORMULA RS 10W/50 - Mobile One 5W/50 - Selenia 10W/60 - Shell Ultra Helix 5W/40 - Fuchs Titan Super Syn 5W/50

Elanlover: From "unknown" to Amsoil synthetic Euro spec 5W/40 - engine and tappets much quieter

ScottJ: Halfords 5W/40 FS since purchase at 115,000 till now at 142,000.

L.G: Shell 5W/40 to Mobil 15W/50 FS

Josler: Mobil One 0W/40. Turbo. Complained of noise. Changed to Castrol Magnetec 10W/40 SS

Johnny: 15W/50 FS (Make?)

LGM: Valvoline VR1 Racing 10W/30 FS Used Mobile 0W/40 FS with good results. Tried Castrol 5W/30 FS but found lifters were clattering for awhile.

The Bard: Mobil 5W/30 FS

Ekapol: From SS Castrol 5W/30 to FS Mobil One 10W/30 engine is much quieter.

Enright: Mobil One 0W/40 FS

Oliver: Elf Excellium 5W/40.

Rambo: Shell Helix Ultra 5W/40

Ultimatt: Reverting back to Mobil One 0W/40 FS

markVasey: From Mobil 15W/50 to Castrol Magnetec 10W/40 - N/A (still burning oil)

Rip: Edge Sport 10W-60 1990 SE Turbo 74000 miles

RayD: Valvoline Syn Power 5W/50 FS, to Valvoline VR1 Racing 5W/50 FS 40,000 miles, SE Turbo

Dico: Mobil 1 fully synthetic 0/40 FS 44,000 miles, Turbo Purchase car 4 years ago at 30,000 miles. Changed oil and filter every 3000 miles.

Sy: Mobil 1 fully synthetic 0/40 70,000 - 110,000 miles, SE Turbo Changed engine about 3,000 miles ago because old engine was burning oil regardless of type.

Clemo: Redline Racing oil. 5W/30 FS Full engine rebuild 6000 miles ago. NA now reading 116000. changing oil and filter every spring . Covering about 900 miles a year. Using Redline MTL gearbox oil.

Martin R: Silkolene 10w/50

Specky: Mobil Super S 10W/40