15W-40 Vs 5W-30 Oil

Mack_1111

What is the difference between the different types of oil? I've being using 15W-40 Oil in my Mk-1 focus, just read in the owners manual that I should be using 5W-30!

Does it really make a difference?

Yep, 15w40 would be for the earliest of the fuel injected, cat converter equipped cars of the early to mid 90s. Better to use the 5w30 as directed. Have you been topping up or doing oil changes with 15w40?

Calling a spade a spade in a Mk1 Focus it doesn't really matter hugely though, no offence to the Mk1 focus but under the bonnet wasn't exactly cutting edge.

Mack_1111

I've done one oil change with the 15W-40 oil and have driven approx 2K miles on it. Any recommendations?

Plug

I'd just wait till the next service and get it changed to the correct stuff. Your not going to cause engine failure don't worry.

Mack_1111

Thank you

Neilw

The 15 part is the viscosity at cold temperatures, 40 is the viscosity at normal operating temperature. 15 would be too heavy at colder temperatures and would not flow around the engine as well as 5w oil.

Mack_1111

I'll be changing it before the winter so cheers

Nissan doctor

Engines with Hydraulic tappets like your focus require the thinner fully synthetic oil which is recommended for your car. Also modern engines are designed with much finer tolerances requiring the thinner oil.

15w40 is far to heavy a grade for a Ford Zetec engine. If you leave that in untill your next oil change you will be well aware of what noisy tappets sound like.

Mack_1111

Cheers, I'll get to it so. Appreciate all the help guys