OILS
The cheapest insurance that you have with oils it to changethe oil filter every time you get to a certain even mark on your vehicle. for me every 5,000Miles on my car/truck I toss the filter na add a new one. I only add enough oil to fill it back to the full mark. Once a year I change it, usually just before summer. Changing the filter gets rid of any junk in the system and allows the nwe filter to catch anything that the old one may ahave let bypass because it was getting full. Replenishing the oil everytime that you change the filter is just that... Synthetic 10-40 in the winter and 20-50 in the summer...I changed right after my fuel mileage topped out. IF you want to have a demonstration of oils ask some friends to bring some oil over, and make sure that the amounts are equal and usea camp stove and put the oils on and see which ones burn up the fastest, timing them and then use a couple of synthetics using the same proceedure...it is a valuable tool in making you use full synthetics all of the time. If you have a super freezer do the same with oils and see how they flow when they are cold...synthetics win again! ANY good synthetic is my choice, I use AMSOIL, but you can get ALmost any brand of good synthetic oil at AutoZone. If it makes you feel good (like Curt) to change your oil at the same time and it only cost and additional $6.00 then go ahead and do it...synthetic is worth it's weight in that ther is less friction, therefore less heat and wear, so you get prolonged engine life...besides it doesn't evaporate like Dino oils do. and its sheer strength is vastly greater than crude oils...I carry a case of filters at a time and when I get to my last two I order another case (12) and I keep them in an old gym locker that I have in my barn...along with oil. If you want to keep your top end lubricated, like in the old days you can add a smidge of Marvel Mystery oil to your gas, or just a shot of 2 stroke oil to your gas...it protects the tank from rust and it wont hurt the carbs because you are using so little of it...it may be over kill but "an ounce of prevention is worth...whatevever...they used to say in the old days...personally I've used diesel on occasion just a very small amount, as it is oil based and as kid we used to take old cars and dump about 6 oz. from an old Coke bottle with our thumb over it and rev the engine up to keep it from stalling and pour it directly intothe carb to clean out the top end and blow out carbon and xrap from the engine...It would smoke liek a couple of dragsters at the track but it would blow out the nastiest amount of carbon that you have ever seen from the exhaust. You can also use diesel to flush the oil system in your car...but that takes a lot of explanation so that you don't ruin the car engine...but it leaves hte engine CLEAN when you are done!