15-40 semi synthetic OK for Jimny?

ASDA selling 4 lt Castrol GTX 15-40 semi synthetic half price £20 for £10.
£21.95 in Halfords (should be Doublefords!) their giude says 10-40 semi synthetic for Jimny.
According to t'tinternet 15-40 has mostly been replaced by 10-40 which has a lower cold starting viscosity but the same normal operating temp viscosity.
Any thoughts or recommendations?

I wouldn't. Jimnys have quite marginal lubrication to the top end, they quickly seize a cam if the oil and filter are not changed regularly.

It should be fine really, but why risk a load of trouble?
There are plenty of semi synthetic 10/40 about cheaper, halfords do a good one, and when they can't sell it you can get a good screwdriver set, or 1/4 drive socket set free.

I take it 10/40 fully synth is ok ?

Unless it is a VVT, I think they like the 5/40, but I haven't got a handbook for them. In general the synthetics maintain their viscosity for longer, and resist higher temperatures. (so they are better ) You really won't notice any improvement though.


Wilkinsons sell a 10/40 semi synthetic for £10.99 for 5 litres.

Actually, you can use a diesel engine type oil, these have better additives, like zinc that reduce wear to crank and cams, and have detergents to clean the oilways and hold dirt in suspension. The reason they are not recommended is the zinc will damage the exhaust catalyst if you are burning oil.

Is it not 10/30 suki reccomends? just after looking in martins Fluid write up?

Or is it no different?

www.bigjimny.com/index.php?option=com_co...nformation&Itemid=63

You are correct 10/30 is the preferred lubricant.
10/40 is fine according to the handbook.

In the uk, 10w40 is our standard motor oil, in foreign parts 10/30 is much more commonly available.

You can get 10w30 motorcycle oil easily enough, you have to pay a premium for 10w30 over 10w40 though.