Oil Change - can I mix grades URGENT

[mr. shr]

Hi All,
Doing an oil change on my W202.

Bought 2 x 5 litres from ECP at the weekend.
Foolishly, I didn't check they gave me two of the same stuff!!

I've just poured 5 litres of the 5W40 Shell Helix Ultra (229.5 spec).
Was just about to pour in the contents of bottle 2 when noticed it's (5W30 229.51 spec)

So can I put the final 3 litres of 5W30 in or is that a big no-no?

Bit stuck really as can't drive to ECP to get it swapped for the one I asked for as car is up on stands with only 5 litres of engine oil in it.

 

[Scott_F]

Hi All,
Doing an oil change on my W202.

Bought 2 x 5 litres from ECP at the weekend.
Foolishly, I didn't check they gave me two of the same stuff!!

I've just poured 5 litres of the 5W40 Shell Helix Ultra (229.5 spec).
Was just about to pour in the contents of bottle 2 when noticed it's (5W30 229.51 spec)

So can I put the final 3 litres of 5W30 in or is that a big no-no?

Bit stuck really as can't drive to ECP to get it swapped for the one I asked for as car is up on stands with only 5 litres of engine oil in it.

Although it would probably be OK to mix the two if you had no other option it is best avoided.

Since the oil will be in your engine for thousands of miles and many months, it is much better to do the job correctly from the start. I would be tempted to order the correct oil online from ECP and use their free delivery service.

Or if you need the car in the next few days, ask a friend to give you a lift to ECP to buy the correct oil (and make your displeasure known when you get there !).

 

[mr. shr]

Well I agree with you entirely.
I've just called them.
Waiting for a call back see if they can drop the right one off for me. They've got vans delivering all the time so don't see why they can't drive by here.

 

[Bellow]

'Dumbelling' is a technique used by suppliers of gear oil where any intermediate grade of oil can be obtained by mixing grades higher and lower in proportion - eg a half and half mix of 10 weight and 90 weight would yield a 50 weight. Only ever done with oils of the same formulation.
By that reckoning I think you are safe to mix grades. Expect a 0W-36ish!

 

[mr. shr]

Update:

All sorted. I called the branch, explained what happened, and they sent out the correct oil in one of their vans.

Well done to EuroCarParts for quick and effective resolution.

 

[mr. shr]

'Dumbelling' is a technique used by suppliers of gear oil where any intermediate grade of oil can be obtained by mixing grades higher and lower in proportion - eg a half and half mix of 10 weight and 90 weight would yield a 50 weight. Only ever done with oils of the same formulation.
By that reckoning I think you are safe to mix grades. Expect a 0W-36ish!

Thanks for this.
I agree that in general, it probably would be ok to do a mix of oil grades.

However, the reason I was doing this oil change was because I had (I think) noisy tappets.
A number of people on the net suggested trying an oil change first, as this might cure the problem.

So therefore I thought it would be better to make sure this oil change was as 'pure' as possible, if that makes sense?

 

[Scott_F]

^^ And has it cured the problem ?

 

[mr. shr]

Sorry, should have said about that too.
I'm hoping that it has.
See here.

 

[m500dpp]

It should help, it's a bit late but Shell also do a 0w 30 which might be worth a try next time - I had a noisey tappet on the wife's 14 year old MX5, 0w 40 Mobil 1 cured it completely.