I have Shell Rotella full synthetic 5W-40 in my truck. I'm in Ontario and get the oil at a Walmart in northern New York state. On my last trip, the Walmart didn't have any Shell Rotella synthetic in-stock. My truck doesn't use much oil, but if I need to add some before my next oil change is it Ok to top it up with another brand of synthetic oil. I can get Moblie 1, Castrol synthetic and Amsoil, however the Amsoil only seems to be available in 10W-30 weight. Thanks

I'd like to know what it could hurt? I mix a gal. 5w-40 syn rotella and dino 15w40 rotella when I change it.

Amsoil also comes in 15W-40

Hi
Amsoil is avaliable in 15w40 and if you are a dealer or perfered customer (membership cost 30$ for a year) it cost 6.50 canadian per liter IF you have a membership, PM me and I'll give you my number and you get it for cost plus shipping, they ship directly to your door. Amsoil is the 40,000Km (25,000Mile) once a year oil change (I personally change it at 20,000Kms) oil samples are the best way to know if the oil is due to be changed, samples are well worth it as you now know the true condition of your oil and engine. A friend of mine with a '03 dodge just did a sample on his oil the oil was tested with 28,000Kms and it still had 70% of its life left, that means he roughly could have went another 70,000Kms!!
Not trying to make a sale on the stuff but I have been using Amsoil for the past 8yrs and think it is the best oil out there, and the Cetane Boost/fuel additive kicks ass
Ps you can mix oils, with no ill effects, apparently as in the case of Amsoil they claim it will shorten your drain interval to the level of the lower "quality oil" or roughly 5000kms
Nick

It's perfectly o.k. to mix different synthetic oil brands. It's also o.k. to mix a synthetic with a petroleum based oil.

Thanks for the replies. I thought it would probably be OK to top up with another brand of synthetic but I just wanted to be sure.
Thanks for you offer Nickg about the Amsoil. I have a buddy in Toronto who made me a similar offer so perhaps I will go that route with his connection.
Jcol