Engine oil spec

Just tells at what temp the test have been done, not at what temp the oil is suitable for, or a max / min.

Gets -15 here but ordinary oil is ok.

The m16 is speced for 0w-20 but i have in my limited wisdom assumed it was the same engine as the m13 so been using the 10w 30 oil. Even in winter. Or was it 5w40..?

wrote:

The figure before the W is the SAE viscosity at 0 deg C.  It certainly gets that cold where I am.

Not true, the figure before the W is considered to be a winter grade and the SAE measure this at a temperature between -15 and -40C depending on the grade, see  en.wikipedia.org/wiki/SAE_J300 .

The chart shown in this link ( penriteoil.com.au/knowledge-centre/Visco...an-sae-viscosity/180 ) is probably as good as you can find and shows 5w30 as suitable between -30 to 36C and 10w30 as suitable for -25 to 36C, both equally as good for any temperatures we see in winter in the U.K.

However, recent high summer temperatures would suggest 5w40 as more suitable going from -30 to 40C.

Robin

 

I thought 0 deg C was in the standard textbook for vehicle mechanics (Hillier) but, checking, that actually just says the W viscosity is at a "sub-zero" temperature, so the author probably couldn't be bothered to look it up!

One advantage of 0W oil is that it should indicate a proper Group IV (PAO) base oil, as it's hard to make a hydrocracked "synthetic" mineral oil meet  that winter rating.  Synthetic *should* mean the base oil has been created by combining smaller molecules to give the exact desired properties, but a legal case in the USA many years ago means any old mineral oil can be labelled "synthetic" after what is often superficial processing.  You can't make a proper synthetic oil and sell it for £20 for 5 litres, as is the case for some of the off-brand stuff in the discount stores.

Not that a gen3 Jimny needs anything better than a good quality 5W30.

wrote:

I thought 0 deg C was in the standard textbook for vehicle mechanics (Hillier) but, checking, that actually just says the W viscosity is at a "sub-zero" temperature, so the author probably couldn't be bothered to look it up!


 

A number of Internet sources, including oil manufacturer's suggest the test is done at 0F (-17.8C), the US ones I can understand saying this, but the high temperature is done at 100C which is 212F, so a nice mix of units if that is actually true.

Anyway 5w/30, 10w/30 or 5w/40 won't make any difference in the UK.  The Jimny is not a high stress engine, so almost anything will do.  I can remember my old motorcycle days, the Hondas I had used a mono grade oil, but my '77 Triumph is like the Jimny, you can put anything in it.

My other car uses a fully synthetic oil and if you read the manual it only specifies one make, which of course is twice as much as anything else.  As I don't do many miles my local garage usually only changes the oil every second year, there is no point changing every year it comes out as clean as it went in.

Robin

I would guess the incredibly thin 0W16 oil in the gen4 is just there to scrape a few tenths more mpg in the WLTP test.  Certainly, if you read the owner's manual, you can use other grades depending on the climate.  I doubt I'll use 0W16 when I come to change it myself.

Thanks for the input chaps