Right now, I am using Rotela 5W40 synthetic. Here in Indiana, the temperature is still fluctuating between 30 degrees and 60 degrees. They are talking about a winter storm watch for tonight! Anyway, I was thinking about switching to Royal Purple synthetic 15W40 when the weather warms up. Any thoughts?

Thanks!

 

RP was good in its day but is nothing special now. The UOA's are average and even top tier dino beats it in the tests. For the 6.50 a quart price tag i no longer use it. Its just not that great. I would stick with your 5w40 rotella.

 

I have to agree. RP is good stuff, but it does not deserve the premium price they demand for it now.

 

Sonic, what were you hoping to gain from the switch?

 

I was thinking that I would have better summer oiling with the 15W-40 than the 5W-40.

 

It's the second number that dictates the hot behaviour of the oil. So in summer operation, both a 5W40 and a 15W40 will be about the same.

Check out http://en.wikipedia.org/wiki/Motor_o...rade_motor_oil for more info.

For 99% of consumer users, sticking with the factory recomended oil will give you very good warm and cold weather performance. Unless you do some very heavy hauling in extreme heat, it's probably not worth switching to a heavier oil.

 

I agree with 77250. Use the correct, recomended weight. What engine do you have? With 5w40 and 15w40, I'm thinking you must be running a Ford diesel? If not, switching to a heavier oil, will reduce your fuel mileage, even in summer. Modern oil, is made to take engine heat, much, much, better than oil used in the 60s, 70s & 80s. You have performance cars, running hot and clean, by design, with 5w20 and 5w30 oils. Thinking you need thicker oil, for summer driving, is "dated" thinking at best. Anyway, post your exact engine details vehicle owned, and I can pinpoint my recomendation even further.

 

Ed,
You are correct in your assumption. I have an '04 F250 Super Duty with the 6.0 diesel.

 

Sonic, excellent choice then. the Shell Rotella T 5w40 oil will deliver peak perfomance for your Ford 6.0 which is a "Stud" diesel, and you'll receive the maximum MPG fuel mileage, your engine can deliver. 5W40 can safely be used year around. 15w40 is fine for summer months if you choose, and whatever you choose in this grade will work well. Royal Purple, Delo 400 (Chevron) and Mobil's Delvac oils will perform. Me? I'd run the 5w40 Shell Rotella T. Dodge owners with the I-6 Cummings diesel, pulling car trailers cross country, horsetrailers 150+ miles one way, all have rave reviews for the 5w40. Regardless, your '04 F250 SD is a great truck. What color is it? Ed

 

Ed,
It is red,extended cab 4X4 with the Torqshift transmission.

 

Beautiful! Keep it clean and waxed. It will give you years (decades) of useful service when properly maintained. Ed