Iīve spent the last couple of hours reading up on viscosities but I canīt find an answer to my dilemma:

My 305 T/A "wants" 10W-30 or 5W 30 of course.

I plan to put synthetic (either fully or blended) in it because it has semi-low mileage and is 100% leak-free. BUT because I live in Sweden, I canīt find any synthetic oil with the correct viscosity grades!!! (Damn european cars fault...)

I will mention that I drive the car in 0-30 degrees celcius and very-rarely below freezing.

My choices are:

10W-40 or 0W-30

Now, Iīm thinking that the latter would be better because the oil is not supposed to be thicker when hot than SAE 30 and the fact that it is thinner while cool really doesnīt matter much because it will just flow easier and reach the entire engine quicker. A 40-grade could potentially have a little bit harder time in reaching all the nooks and crannies in the engine.

Am I completely wrong in this? I know some of you use 15W-50 with good results but I donīt race my car so....

As always, any tips appreciated as I have to get the oil tomorrow morning because Iīve been planning a "tuneup weekend"

 

Mobil1 10W30 or 40 (don't think them make a 40) but a 10W0 should be fine, it would be better then a 0W30 oil. Alittle haevier in a synth is better as it works out to almost the same as the dino oil of a lesser wait.

Mobil 5W-30 or 10W-30 ar my two choices but another synth in th 10w-40 range will work fine

 

I canīt even get Mobil 1 in the correct grades here. Euro cars all seem to run 0-40, 10-40 or higher (0W-60 anyone?) so I guess they donīt see a large enough market for t here. Mobil 1 seems to have one type of 5W-30 oil on their Swedish site...but I canīt find it anywhere.

Not that Iīm gonna do this, but I wonder what would happen if you mixed 0-30 and 10-40...? (Like I said...I am not trying it...!)

 

i run 5w-30 or 10w-30 in cold weather and 15w-40 or 20w-50 in the heat. the big reson behinf gm saying to use what it says has notihng to do with engine protection abnd everything to do with gas milage. from what i've read or heard you're ahead to blend your own oil thasn run a blended oil because it's mostly dino with a little synthetic.

 

Well, I ended up going with Castrol GTX 10W-40 synthetic. Tthe engine was so tight that it was completely dry underneath!

I just put in 40 or so miles after the oil swap and everything is looking good...