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MG Midget and Sprite Technical - Engine oil

I am finding it more difficult to get 20w/50 engine oil.
Most of the shops here sell 15w/40,would this be ok to use or not?
1275cc MK3 1972
manian

Hi
Our A series engines (and gearboxes) were designed for straight 30W oil.

The further away from that original 30W you get, the more likely that you could have trouble with it being too thin for your bearings and clearances, leading to wear.

However, modern oils are all lightweight, with additives that make them behave like thicker oils when heated up. In the case of the two examples you mentioned above, 20W and 15W, respectively, stock oils are used, and then additives are added to make them act like 50W and 40W when hot.

These additives tend to break down over time, so changing your oil regularly will go a long way to avoiding a problem. The thinner the base oil, the more often you ought to replace it.

One way to look at it is this: if a 20W-50 oil averages out at "35W", and a 15W-40 averages out at "27.5W", then you can see how the thinner oil gives you a little bit less margin from that 30W target as those additives wear out.

The fact is that there are a lot of folks out there who run thinner oils in A series engines, and they claim to have had no trouble. Also, we tend to change our oil more regularly, and at lower miles than folks did when these cars were "just old cars", so that makes a (good) difference in whether this is a big problem for us or not.

In any case, realize that you are using a thinner oil, so you ought to change it often to avoid unnecessary wear (say, every 3000 miles).

Also, make sure that the oil you use has zinc in it (modern auto oils have eliminated this, but it is necessary for our old fashioned lifters to control wear). Many of us use either motorcycle oil, or diesel oil, since these two tend to have the ZDDP we need, and are more readily available in our desired 20W-50 grade.


hope this helps,
Norm
Norm Kerr

I wouldn't use a 40W though a lot depends on how hot your car's engine gets how you drive it (oil surge under braking, cornering etc).

Can't you get any Mobil 1 15-50?
Daniel Thirteen-Twelve

like Daniel I wouldnt use it either

I might use it to top up whilst I drove round to find the proper stuff

bill sdgpm

Try to find Valvoline Racing VR1 20W50...it already has ZDDP in it.

Maybe this will help:

http://www.valvoline.ee/contacts/contacts.html
Dave Rhine ('78 1500)

Something i learned the hard way-
dont use synthetic oils.
The guy at the auto parts store sold me synthetic oil without knowing that it was for a midget and i didnt know how bad it was. Now my car is burning a decent amount of oil because the synthetic stuff can sneak past the cylinder rings into the combustion chamber because it is slicker than regular oil and so it coats the cylinder walls and gets left in the combustion chamber and burns, making the engine hesitate really badly.

Ive learned my lesson. Never again.

I told the guy yesterday that he sold it to me and he was really frustrated with himself and really apologetic.
Seth Brecklin

Synthetics can also create gasket & seal leals you didn't have before!

If you've been running conventional oil, stick with it...had to pull & re-seal my oil pan after trying a semi-synthetic blend.
Dave Rhine ('78 1500)

don't think you should blame the oil - I've run my two race engines on either 5/50 or 15/50 fully synth Mobil 1 for 5 years and they don't burn oil. One of them does not leak a drop either.
David Smith

Seth Brecklin and Dave Rhine - I've run my Sprite on Mobil 1 for over a decade on 2 engines of which the first one had 2 (freshen up) rebuilds during its life in my Sprite.

I NEVER HAD AN OIL BURNING PROBLEM USING A SYNTHETIC ENGINE OIL.

In fact I do have a really tired 1275 engine in my garage that while down on power, still wasn't burning oil when I pulled it.
Daniel Thirteen-Twelve

Were the engines high mileage when you FIRST started using synthetics, or freshly rebuilt?

It does make a differnce.

I totally agree with synthetics in new or newly rebuilt units, but changing fron conventional to synthetics in mid life is asking for leaks.

All my vehicles that I've had since NEW have known nothing but Mobil 1 after break in.

I love the stuff, it's great!

All I'm saying is, if you change over in an old engine that's known nothing but conventional oil, you will most likely have leaking problems.

Each to his own...

:)Dave

Dave Rhine ('78 1500)

This thread was discussed on 03/04/2010

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