Quick Engine Oil Question - First Service Pending

ChrisG · Post by **ChrisG** » Tue Oct 02, 2007 6:31 pm

Hey Guys,

My first service is booked for Thursday (Elise R). While in Costco today, I had an impulse buy of Mobil 1 0W40.

I did telephone MMC prior to buying to ask what they would have been putting in and was told 5W40.

My question is am I ok using the Mobil 1? Am I right in thinking the 0W bit just means it is less viscous at low temps? Any warranty issues with this?

Worth mentioning MMC first service labour is free but they quoted £60 +VAT for the oil. Costco was £23 for 4 litres of Mobil 1, I bought two.

Any advice appreciated.

Clarkie · Post by **Clarkie** » Tue Oct 02, 2007 7:28 pm

Don't think there will be any warranty issues but it's worth asking. They should be Ok with you using your own oil but it's worth asking again. MMC changed my brake fluid to SRS which I supplied free issue, and didn't grumble.

ChrisG · Post by **ChrisG** » Tue Oct 02, 2007 8:29 pm

Clarkie,

Thanks for the reply. Graeme at MMC did say I could supply own oil. My concern was more with the spec of the Mobil 1.

Chris

Clarkie · Post by **Clarkie** » Tue Oct 02, 2007 8:51 pm

Can't remember the relationship between the numbers in the grade but recall the closer together the better. The handbook says 5W40 so 0W40 shouldn't make a huge difference. I changed the oil in my car for TT2007 to Mobil 1 15W50. Checked with Ali at MMC before the change and he said it would be fine for the summer.

steve_weegie · Post by **steve_weegie** » Tue Oct 02, 2007 10:03 pm

ok.... here goes.....

the difference between the numbers relate to how the oil flows when its cold and when its hot.

A 0W-40 oil flows like a 0 weight oil when its cold. 0W is measured at somthing around -26C
it flows like a 40 weight oil at 100c

The difference in the numbers relate to how many polymers the oil contains - as the polymers react to the heat, they gloop up and stop the oil from thinning out. The problem is that when you have a very large difference between the numbers, you're relying heavily on the polymers working correctly to prevent your oil from thinning, ie a 5W-50 oil relies more heavily on polymers to behave like a 50 weight oil than a 15W-50 oil does.....

The problems start to arise when the oil gets older... Polymers break down and dont react to heat anymore & you end up with an oil that's thinner than you expect it to be.

Mobil 1 is excelent oil & you'll get on fine with the 0w-40 or the 15w50 stuff.... IIRC mobil dont to mobil 1 in a 5w-40 but i may be wrong... as im on the wrong end of a few pints in .london

gdr · Post by **gdr** » Wed Oct 03, 2007 8:08 am

There is a Mobil fully synthetic 5W-40, not commonly available from Halfords etc, but can be obtained from outlets like OPIE Oils, don't think it is called "Mobil-1" but presumably same quality. Used more by the trade I think. Check with MMC as regards warranty before you use oil that is not as per book though.