Originally Posted By: BigJohn
I hear a lot of people on this forum talk about the need to use 30wt instead of 20wt, when towing. So here's the question...
Hasn't Ford, in their 1/2 ton pickups, spec'd 20wt for several years? I wonder how service trucks are performing with 20wt. For instance the oil and gas industry uses thousands of these trucks in the oil field. Also, cities and counties across the nation have fleets of these pickups....
Surely there is data somewhere.....????
I do have to admit that I would lean to 30wt in summer and when towing....so I am in that camp until some data surfaces that proves it wrong.
You have to remember that all of these generalizations will NOT lead you to the proper answer for your vehicle. A Toyota 4-Runner is not a Ford F150. Oil temperatures may be different under heavy loads, from the winter to summer, etc. Different vehicles are just that... Different.
I believe Jim Allen enlightened this board with data from his F150 V8 stating that under all kinds of different conditions, his oil temperature did not even reach boiling point. It was even colder in the winter, even after prolonged driving. This has a huge impact as to why many Ford F150's work very well with 5W20!
You would need to do the same with your 4-runner in order to conclude that you also would be safe with a 5W20 as opposed to a 5W30 in all of the conditions that you encounter. You might find that you would be absolutely safe, or you could find that when towing with your rig the oil temps get a bit higher than you'd like to see with a 20 grade in there.
Different cars... Apples to oranges...