Embarrassing mistake

Snickers Man

A "friend" (honest) has just realised to his horror that he has put lubricating oil intended for a diesel engine into his petrol engined car. :o:o

(NB NOT diesel fuel into the petrol tank; lubricating oil only)

Is this a disastrous mistake or will he get away with it? Should he drain all the engine oil and replenish immediately or will he get away with it for a few hundred miles? (Big journey planned today)

Some people :rolleyes::rolleyes:

Alanstrainor

What oil specifically?

If he has changed it once, it shouldn't be too painful to change it again to the correct spec to be honest... I'd drain and replace it.

Aint Eazy Being Cheezy

Depends on the car tbh but I wouldn't even bother chancing it. Undo the sump nut, let it drain out, then refill. Won't take 20mins.

REXER

If it's the correct grade and spec of oil he should be alright.
Oil for diesels has added detergents to help keep deposits from building up so it will help him clean up his act.

Snickers Man

VW {Passat 12+years old) It wasn't a complete fill. Just a top up. But the oil was fairly low when "he" put it in.

Snickers Man

Oil was 15W 40 grade

jimgoose

One can have too much of a good thing. Diesel-specific oils have more/more aggressive detergent blends and ZDDP in them, which might attack everything and anything from piston rings to cat-converters. It 'twas me I'd get that stuff out of there.

Neilw

Snickers Man wrote: »

Oil was 15W 40 grade

What car is it?

There wouldn't be many if any modern petrol or diesel cars that would use a 15w40 oil.

Second Toughest in_the Freshers

how did he get on anyway OP?

macplaxton

It'll be grand. look at the back of the container at the SAE specs and petrol engines will also be covered I bet.

15W40 isn't exactly thick either. It's not like the temps here are so cold it'll be a problem.

Neilw

macplaxton wrote: »

It'll be grand. look at the back of the container at the SAE specs and petrol engines will also be covered I bet.

15W40 isn't exactly thick either. It's not like the temps here are so cold it'll be a problem.

Not true, some cars a very sensitive to the type of oil used, vw tdi's and fords for example.
Best to stick with what's recommended.

There is quite a difference in viscosity between a 0w and 10w, and 15w thicker again.

jimgoose

The "10W-40" numbers are grades, not viscosity ratings. Viscosity is measured in units called Centistokes, and most modern engines like oil with a viscosity somewhere between 10 and 14cSt to maintain good flow and pressure - both quite important for lubrication. Common or garden 10W-30s and 10W-40s repsectively have viscosities of around 10-11 and 13-14cSt at 100C, full operating temperature.

The number before the "W" is an indicator of how much the oil thickens when cold, and I can tell you now that they are all more-or-less useless during cold-starts, hence the importance of the warm-up routine. By way of illustration, any "10W-" oil will have a viscosity of about 100 cSt at 24C. That's TEN TIMES what the engine wants at operating temperature. See the problem?

But some are rather less useless than others. A 0W-X0 full-synthetic brew is about as good as it gets. An "0W-" oil will thicken to around 40cSt at 24C.

greasepalm

last time i used 15w-40 must have been in the early 90s,changed to 10w-40 then.wonder where he dug that old oil out from.

9935452

Just do an oil and filter change for the correct oil .
He will have then have a service done for the next 5/10k miles then