I have a 2018 GMC Sierra with 5.3L engine, is it safe to switch from 0W-20 to a 5W-30 synthetic engine oil to make it last longer?
Why do you believe that will make your engine last longer? Any test data to that effect?
no
You might find this video from an oil expert going over the actual data to be of interest:
"Trust data you can see and not claims you can't."
I have a 2018 GMC Sierra with 5.3L engine, is it safe to switch from 0W-20 to a 5W-30 synthetic engine oil to make it last longer?
If the engineers who designed the truck wanted the engine oiled with 5W-30, they would have designed it that way from the start. Using too heavy of an oil will wear the engine out just as quickly as using too thin of an oil.
If the engine was designed to cold start with 0-weight oil, and you put 5-weight oil in, the oil pump will take longer to build pressure. A running engine and extended time for initial lubrication equals premature wear every time.
It doesn't stop there, either. The engineers designed the engine to require a 20-weight oil at operating temperature, and you're wanting to put 30-weight oil in. The oil you're considering using is more viscous, that translates to increased stress on the oil pump. Your hydraulically actuated variable valve timing may also be affected. Modern oil journals are extremely tight, and the heavier oil does not flow as efficiently as thin oil.
Cars aren't like my '79 Pontiac Catalina anymore, where you could use a range of oils based on ambient temperatures and whether or not you frequently drive on the highway. I use 10W-40 in the Catalina because I tend to drive on the highway a lot and that car doesn't have overdrive. Thicker oil helps wick away heat more effectively. Your truck has at least one overdrive gear; it doesn't build up nearly as much heat.
If your mileage is getting up there, switch to 0W-20 high mileage oil, that's it.
