We had a 1993 Ford F150 e. Cab 4X4 ruck at work that had the wrong dipstick in it. 302 engines in truck used 6 qts and in cars 5 qts. It would always read over full when it had the required 6 qts in it. I inquired at the Ford dealer and they confirmed that many truck engines come with the wrong dipstick and not to use that when changing oil, follow what the manual says.
My neighbor had (he deceasaed now) 1990 Buick Park Ave. The manual said somehting like 4.5 qts with filter but the quick lube place would always install 5 qts and charge him for that. This must have went on for years becuase one day about 5 yrs ago he asks me to look at it and tell him what I think. It looked like it was way over the full mark but in reality was only 1/2 qt over. He showed me a lot of receipts going back several years where it listed 5 qts. He was po'd and I rode over to the place with him to complain. They assured him that it did not matter one bit that it was 1/1 over so on to the Buick dealer, they said the same thing. He used up about 3 hrs of time, got very irate about this and was worried his car was going to have problems. Did it, NO. His decendents still have the car.