Hi there..

I have seen a LOT of this oil threads but still I ain't sure about what oil to choose on my engine. Just wanted to hear some opinions:

I have a newly rebuild 87 305 TPI engine which have some modifications such as cam, headers, new pistons etc.etc.

The car is used most summer and spring time and not in the winter.

I know that the stock oil viscosity rating should be about 5w-30 and I also now that 5W is the oil "thickness/weight" on cold starts so basically that one doesn't matter as much since I am going to use the car mostly summer time.

I am just a little bit unsure on the "warm" engine oil viscosity like the 30 number on this oil type. The oil stores around here in Norway have 5w-30 synthetic oils but they are the most expensive oils. So my question is could I buy for example 5w-40 and run that on my engine?
I want to use synthetics since the engine is freshly newbuilt.


Are here any oil-experts that could give me an advice?

By the way I have drove about 1000miles on regular 10-40 mineral oil under the engine break in period. So now I want to change the oil and filter and use synthetics from now on...

 

10w30 is what I would use.

 

I use Castrol GTX 10w30, and that's what I suggest you use, I have to agree with cralt.

 

I woulndnt use synthetic till the motor was broke in, and I would use mobil 1, yes it cost more but if you want REAL synthetic use mobile one. See here in the usa oil is not regulated like in say germany. Int the usa we can make oil mix it with a little synthetic and call it that. But in germany the are very tight on emmisions and the oil that is sold as synthetic is 100 percent real and can you guess that there is only one true 100 percent synthetic oil? yep mobil one, if you have doubts go look it up. but that is the only oil i will ever use......

 

Is the 5W-30 more expensive than the 5W-40?

A 5W-30 would be fine. Not all synthetics are created equal, so without knowing more details, it's hard to say much more than that. Typically, though, it's better to keep the spread between the two numbers as small as possible. A 30 weight is all you need for warm temperatures, but all else being equal, a 10W-30 would be preferred to a 5W-30.

 

Sounds like that's covered.

 

with 5w30 you will get better gas milage,

 

actually the engine oil is a 30w viscosity when it is cold and then the 5w viscosity when the engine is hot. from all the reading i have done and experiences as being a mechanic i use a 10w-30 all year round. but i live down south.

 

i use 20-50 on my bolt on 350tpi