I have been into engines that have used penzoil all thier life and they were clean. Not sludged up. The custmers changed oil regularly and drove the vehicle around 50 miles each way to work and back. The reason I had to open one up was someone was kind enough to drop a piece of metal down his carb and ruined a piston. The othere had too many miles to count and had flat worn out.
I opened up a Chev 305 that had Mobil 1030 from new, changed every 3,000 miles and you had to scrape the sludge out. At 65,000 miles the engine had to be replaced. But it was started, driven 1 1/2 miles and shut off for the day, then 1 1/2 miles home. Never warmed up. Say what you want about Penz. but I have had very good luck using it. But I change oil when needed, and my vehicles get driven rather than just short trips.
