Towing AFTER First 500 miles...Oil Change?

SoCal Angler · August 14, 2023

My new 2023 GMC 3500HD 6.6L Gas and 6 Speed Auto:

Manual states to "perform the first oil change before heavy towing." In addition, "Do not driver over 50mph and do not make starts at full throttle during the first 500 miles of trailer towing."

What is considered "heavy towing, as manual does indicate a weight amount.

I need to trailer my boat (2500# GVWR) about 150 miles round trip, soon after I reach 500 miles. Wanted to know if I need to change oil prior to this tow.

Thanks

Another JR · August 15, 2023

I’m always an advocate of, at a minimum, following the break in advice in an owners manual.

That said, if your trailer only weighs 2500 lbs and has a frontal area less than the truck, I would not be worried about either of those recommendations if you for some reason can’t follow them. Just take it easy while accelerating and while pulling your boat out of the water at the boat ramp.

The engine oil recommendation is to ensure you have clean oil and get rid of break in particulates before you run at high cylinder pressures. You probably would be just fine not changing it but I’d do it if I could. My oil was changed at 300 miles due to my discovery of a dented filter. My truck at 10k does not appear to use oil between oil changes (less than a pint in 4k). Did that early oil change help make it be one of the engines that doesn’t use two quarts between changes? Maybe. I suspect it had more to do with my receiving the truck with 2 miles on it (no test drives by others) and my being easy on it for the first 1000 miles.

The recommendation about initial towing weight and easy accelerations is primarily to avoid damage to the ring and pinion gear teeth in the differential and avoid excessive differential oil temperature. At 500 miles the gear contact areas are still forming and the contact areas are small. Trying to transmit too much power through those small contact areas can cause oil film breakdown and damage to the teeth, and it generates a lot of heat which also can deteriorate the oil and cause oil film breakdown. Ideally you don’t want to tow a heavy trailer before the ring and pinion gears have developed mature contact areas. 2500 lbs is not going to be a problem, though, after 500 miles of initial break in. There are guys who will say “I bought my new truck, drove it home, hooked up my 15k 5er and floored it up and down the Ike for the next 6 months, and my diff didn’t explode. What are you, a wimp?” But if you want a nice quiet rear axle at 150k miles, try to follow the break in advice.

Edited August 15, 2023 by Another JR
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