92-96 Camry: Sludge? Common Problems?

OK - I went to a parts store after work - looking for some tools. Then I had a look at the "high-mileage" motor oils (from memory):

Valvoline MaxLife 5W-30, 10W-30, 10W-40, 20W-50 Valvoline MaxLife Synthetic 5W-30, 10W-30, 20W-50 Chevron High Mileage 10W-30, 10W-40, 20W-50 Havoline High Mileage 10W-30, 10W-40, 20W-50 Pennzoil High Mileage 10W-30, 10W-40, 20W-50 Quaker State High Mileage 10W-30, 10W-40, 20W-50 Mobil Drive Clean Plus 10W-30, 10W-40

Of the "high mileage" oils I saw, only the Quaker State one didn't carry the API donut. The newest (2003) label didn't even claim that it met any API service rating "for performance" like an older bottle (2002) did. I find it a bit strange, since one would think that Pennzoil and Quaker State would have consolidated their formulas when they merged. Now they're part of Shell Oil (AKA Sopus Products).

There's a lot of consolidation going on. The ExxonMobil merger has resulted in the same unique bottle shape for conventional Mobil oil and Exxon Superflo. I'd be surprised if the Havoline and Chevron Supreme oils aren't the same since the ChevronTexaco merger.

This is true. But for YEARS, Amsoil lied about the reasons that they did not have API approval on most of their oils. They came up with all sorts of ridiculous excuses about being afraid that their formulations would be stolen, that approval was too expensive (it's very cheap), etc. Finally an Amsoil employee let slip the issue that they could not meet the API standard because the level of one of the additives that they put in was too high, and would shorten the tine that the catalytic converter would function properly. Ironically, Amsoil's non-API oils provide real benefits for vehicles without catalytic converters, i.e. snowmobiles, etc. It was only after all the hullaballoo regarding lack of API certification, that Amsoil came out with their XL-7500 line.