I'd like to inject a couple comments of value as you guys continue your conversation.
Back in the mid '80s I watched two coworkers flush the oil on large cars they bought cheap when gas prices went way up. One was a late '70s Impala and one was a Continental. They dumped a quart of transmission fluid into the oil, then drained and changed it a few days later. I never had the guts to try that, but it apparently had worked for them on other engines.
In 1976 I bought a used '72 Dodge Dart, 318, 60,000 miles. Had to replace the valve cover gaskets and found 1/4" of sludge build up inside them. Installed a bypass oil filter that used a roll of toilet paper. Years later had the valve covers off again at 120,000 miles. They were spotless that time. I still use one of those filters on an '80 Volare.
Given the continuous improvement in oil, I have a suspicion sludge will be taken care of with regular oil changes. If you look at the ratings on the container, you'll see something like "SE" or "CF". The "S" stands for "spark ignition engines", and the "C" stands for "compression ignition engines", (diesels). The second letters become the next one higher when a significant improvement occurs, often to meet engine manufacturer requirements. Back in '87, the ratings were around "SD" or "SE". What that means is unless you have a stash of really old "new" oil on the shelf, anything you can buy today is going to go way beyond the requirements for your engine. There's detergents, dispersants, seal conditioners, anti-foaming agents, and corrosion inhibitors that are all being improved all the time.
I have an '88 Grand Caravan with a knock in the engine that I thought was going to be fatal, so I wasn't about to waste money on oil changes. As an experiment, I didn't change the oil for over 14 years and 260,000 miles. I did replace the filter every year, and I added a quart every 1,000 miles. Word was there's enough additives in one quart of oil to keep the engine happy. I was still getting three quarts of additives every 3,000 miles. That van dragged an enclosed tandem axle trailer to an old car show swap meet for 15 years. The trailer was bigger and heavier than the van. The 3.0L Mitsubishi-built engine has a reputation for a rather weak lower end, yet it held up to this abuse until the van got so rusty, the carpet was the only thing holding the front and rear together.
What you might consider, rather than flushing the oil, is just two or three oil changes about 500 miles apart. Most sludge will be dissolved right away, then that will be held in suspension and circulate until it is drained out. Little more sludge will be cleaned away once the oil is holding all it can, so draining it out right away lets you start with a new batch of clean oil sooner. Be sure to replace the filter each time. Some contaminants can solidify inside the cool filter and block it, then the oil has to flow through the bypass valve and won't get filtered.
Monday, March 14th, 2022 AT 4:41 PM
