True. I have a late model year 2004 Duramax. The earlier ones had the fill tube sized for the car sized out front nozzles. With my model, and I assume ones after it, the fill tube was bigger so you could go out back and fill up with the big boys. Just use caution on topping off, those big boy pumps really flow some fuel.
Since we're adding stories...
On my first move from Florida to Indiana (late 90's?), I drove a Penske. The first few hundred miles were painful... the truck was extremely slow to react, I couldn't really get up to speed without a mile or two of "runway", and all I could think was "this is going to be one painful 1,000 miles!". Within a few miles of the first fill-up, the truck suddenly started pepping up. I could accelerate, I could actually hit the governor speed! Spoke to the guy when I dropped it off, he said it was likely the last person to drop it off filled the tank with regular because at the time it was quite a bit cheaper than diesel. The engine never blew up, but it was a pig until that regular gas was out of there.
Oh, I also noted an extremely hot leg a few miles form the pick-up point. I couldn't figure out where it was coming from, but I couldn't continue to drive like that (it wasn't just hot, it was starting to burn my leg!). After dinking around with it on the side of the road, I figured out the engine cowling inside the cab had not been properly sealed... the rubber gasket was folded under, so the heat of the engine was being blown right at my legs. Not a good way to start a 1,000 mile trip.
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