on my last service the reciept said they used "5 ltrs millers full synthetic" it doesn't give a 10w40 type rating on the invoice.

what rating oil is it likely to be? should i keep using that oil to top up or is there anything better?

what specifically would the oil be and where is the best place to buy?

 

Millers make loads of different synthetics, some ideal, others not for your car. The only people that will know are the garage.

What year is your car, is it standard or modified and what does it get used for?

Cheers

Tim

 

its a MY99 (RB5 WR), it's been remapped and few things like decat and induction but nothing major i think.

what does it get used for? ..spirited driving?

 

In that, I'd go for the Millers CFS 5w-40, 10w-40 or XFS 5w-40. The other one they make that's suitable is the CFS 10w-50, but those are the only ones I'd use.

Cheers

Tim

 

does it matter if for example they used 5w but then i put 10w in? the invoice doesn't say and i doubt they'd remember if they didn't put it on there in the first place.

 

I would ask them. That said mixing viscosities isn't that bad as long as you use the same brand. Different brands use different additives that can react adversely. Same brand viscosities generally only differ in polymer content (viscosity index improvers). Be mindful though that the resulting viscosity will be slightly different from the oil already in the car and the oil you've added.

 

As said its worth a try asking them before you go shelling out £££ to replace it because you don't know what's in it.

What is making you query the oil viscosity??