I've found that any engine that has more than 30,000 miles should be flushed before using AMSOIL. AMSOIL is a high-detergency oil and will quickly clean most engines. As a result, there is often the situation where the existing build-up, especially if a paraffin oil had been used in the past, over-burdens the oil filter. Although flushing with AMSOIL engine flush helps reduce this, it's not like taking a putty knife to the crankcase. The oil cleans over an extended period of time. I always recommend on any engine with more than 50,000 miles to first replace the existing filter (don't drain the existing oil) with a cheap filter, add the engine flush, and then idle for 20-30 minutes. This places much of the deposits in the new, cheap filter and this way you are not over-filling the crankcase, always a bad idea. After the 20-30 minutes, drain as-long-as-possible, and then install an AMSOIL filter and AMSOIL. After 1,000-1,500 miles, change the filter out, as much of the dirt will already be in the filter, and put a new, fresh filter on.

I've talked to many people that have changed from one oil brand to another (synthetic or petroleum) and after a couple thousand miles find that they are using oil and maybe their engine is smoking. They get mad at the new oil, change the oil and filter and the problem goes away. It must have been the oil, right? Wrong! The filter got clogged with the build-up of varnish (even present when obvious sludge is not) and this coats the filter element making the by-pass valve in the filter click open prematurely. The circulating of unfiltered oil causes contaminants to build up behind the rings and blow-by is increased dramatically. Results: oil consumption. All they really had to do was change the filter.

For this reason, high mileage engines should have a filter change, possibly several, in the first 3,000 miles on AMSOIL. After two or three filters, then they can get into the extended drain ritual safely.

Keep in mind on high mileage engines that cleaning varnish and sludge from the seals sometimes will cause a leak until the seal re-swells. With valve seals, however, they sometimes crack because they've been dry for so long and never do re-seal. The sludge had created a "false seal" which, when removed, will cause on-going problems.

For this reason, I discourage switching to AMSOIL in high mileage engines (I define high-mileage in gas engines as over 200,000 miles and diesels over 600,000 without rebuild) unless the owner really wants to protect an engine, recognizing the risks of leaks, to avoid a rebuild. I know of many people willing to accept this situation as the engines and cars they are in are classics and are not run much. Also, diesel rebuilds are so expensive, feeding good oil through an engine is a lot cheaper and will extend the life overall and reduce the cost of eventual rebuild. Many people start using cheap oil when a car or truck starts using oil, but you are only accelerating the problem.

This is not to say that if you have been using AMSOIL or even another synthetic that you should switch to conventional oil just because you are reaching a high-mileage figure. Any synthetic oil is better than any conventional oil (assuming it is synthetic and not a conventional oil with only "synthetic performance" or synthetic properties, as some companies advertise). If you have been using a synthetic oil and want to change to AMSOIL, you will only improve your position.

As for the additives in AMSOIL, that is proprietary info and I don't know that it is relevant, except to the extent that the TBN level of oils are a good measure of an oils ability to clean and keep an engine clean. The TBN is basically an oils ability to neutralize acids in the oil, a by-product of combustion. AMSOIL's ATM Product Code 10W-30 has a TBN of 11.4, which is quite high compared to others. You are probably on the right track with Esso's Diesel oil which likely has a comparable TBN, although I don't know their TBN, (our Product Code AME 15W-40 Diesel Oil has a TBN of 12). Most gas engine oils carry a TBN in the 6-7 range, hence their 3,000-mile/3-month oil change recommendation. AMSOIL's high quality and quantity of additives have proven to stay up to speed for 25,000-miles/1-year, and with the use of oil analysis to monitor engine performance and oil condition, much longer. Remember, however, you still need to change the oil filter.