Fully synthetic oil

[paddyk]

Hi Can anyone help?
Am I correct in thinking that if you use fully synthetic oil in your car - you can only top up using the same thing i.e fully synthetic ?
Would it damage the engine if you topped up with semi-synthetic as my friend says it wouldn't make any difference.

[AlBags]

That's what one is supposed to do .. yes.
No .. semi top-up will hardly affect its properties at all.
You will get more benefit from changing oil/filter regularly.

[DTCwordfan]

absolutely as Al says - a fully syn is unnecessary in any aged car. What model and age, paddy?

[Toureman]

As al says it won't make much difference but you are slightly degrading the fully synthetic oil doing this, why do it for the sake of a small amount of cash?

If your car is a high perfomance new car it could be a big diference.

[old-wos-is-name]

I was just about to buy fully synthetic in Halfords, and the assistant stopped me and said had i checked that it was o.k. for my car ( 2.0 ltr mondeo diesel.) we checked the reference sheet and it should ONLY use semi synthetic. Idon't know the reason for this, I assumed fully syn was the ultimate oil because it was expensive.