Mobil 1 5W30 has been the factory-fill engine oil on Corvette since 1992. In fact, at one time, Corvettes all had a trim plate under the hood that identified M1 as the factory fill oil.
Interestingly, Corvette Owner's Manuals and Service Manuals have never specificied Mobil 1 by name, however, since 1992, with exception of '92 ZR-1s, they've specified either 5W30 or a 10W30 engine oil meeting GM spec 4718M which generally defines a synthetic oil.
There are other synthetics which meet GM 4718M and, at this point in time, since 4718M, in some ways, is an obsolete standard--given that oil formulation technology used by refiners can make products that surpass that 90s era spec. Because of that there are synthetic engine oils, mainly those which use ester base stocks, which are better than those meeting 4718M, but, because of the obscenely high cost of gaining GM certification, their makers choose not certify them to the standard.
The reason GM specifies a 5W30 has more to do with meeting Federal fuel economy standards and appearing to be a good corporate citizen than reliability/durability or performance. Thus, the best oil choice for just about any Corvette (other than those which are heavily-modified or are race only) is a 10W30. Mobil 1 makes a very good 10W30 and I see it at some Costco stores for a reasonable price.
The best 10W30, in my opinion, comes from the Red Line Synthetic Oil Corporation but, admittedly, it's more expensive. It also does not meet 4718M because Red Line chooses not to certify it due to the expense and that certification effectively prohibits continuous improvement of the product.
Bottom line: if you want your C4, 5 or 6 engine to run hardest and last longest, switch from a 5W30 to a 10W30. Mobil 1 is good. Red Line is better.
As for C5 oil filters, the best on the market is the UPF44. Interestingly, the UPF44 is the only part number left in a short-lived line of premium oil filters GM called "ACDelco Ultragard". Several years ago, ACD launched Ultragard but, generally it was a commercial failure. Ultraguards were expensive and, like a lot of GM's aftermarket products, they were not well-marketed but...those filters were absolutely the best on the market. The entire line was made by Champion Filter Co, which makes premium, private-label filters for the likes of the "K&N Performance Gold" and "Mobil 1 Oil Filter" brands.
I'm not sure why ACD still sells the UPF44 but it may be that it knows the UPF44 is a significant improvement in filtering over the PF44 and/or that the UPF44 is the only Ultraguard which experienced high demand. In any event, there is no other filter on the market for a Gen 3/4 engine which is better and few can equal its combination of excellent filtering ability, low restriction to oil flow and good bypass valve control.
The UPF series of filters is so good that, several years ago, when all of the UPFs except the '44 were being discontinued, I bought several hundred dollars worth of remaining stock of UPF52 and UPF1218 from several dealers arond the country. As a result, I'll use UPFs for many years.
Executive summary: ALL my cars which have cats use Red Line 10W30. The two cars without cats use Red Line SAE30 Race Oil. Any of the cars which see more than 10,000 miles annually, use extended drain intervals. As for filters, I use either the UPF44, the UPF52 or the UPF1218 on all but one car. The remaining car uses a Mobil 1 Oil Filter because there never was a UPF number released for its engine.
ad Do you go strictly by the DIC or do you change it once a year or change the filter every 5k?
