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Today in the Master Auto Repair auto care blog, we’re going to talk about oil change intervals. It seems that as engine technology advances, recommended oil change intervals have gotten longer for Master Auto Repair customers. High quality oil in a well-engineered sedan engine has lead to extended intervals. But it’s also lead to some confusion among St. Louis drivers.

The old mantra “change your oil every three months or three thousand miles, whichever comes first” once applied to every vehicle in your garage. Time and miles take their toll on motor oil. But now, you could have a different oil change recommendation for every car or truck you own.

St. Louis people are like everybody else, they have a tendency to put off all the oil changes to the schedule of the vehicle with the longest interval. Of course, that can lead to problems. For example, recently four of the world’s largest auto manufacturers shortened the published intervals for several of their engines. They originally published intervals that extended out to a much as 8,000 miles.

In real world St. Louis driving, the oil started to sludge up before the recommended change interval. Oil sludge is a thick jelly-like substance. Quite literally petroleum jelly – like Vaseline. This goop was clogging sedan small engine passages so the oil wouldn’t flow to some parts of the engine. This resulted in engine damage. We see it from time to time at Master Auto Repair.

The manufacturers began to offer an extended warranty to cover sludge damage. But there was a catch: the vehicle owner had to follow a new, lower service interval, and provide proof of oil changes in order to make a warranty claim.

So here’s the problem. With longer oil change intervals, it’s extremely important to follow them closely. Back in the day of 3 months or 3,000 miles, if you went an extra month or an extra thousand miles, your oil was still fresh enough that it didn’t have time to build up much sludge.

But if your recommended interval is 6,500 miles and you go over another thousand, you’re getting into heavy sludge territory. You absolutely need to follow mileage intervals very closely. And don’t forget your severe service schedule. If you do a lot of stop and go driving in MO, short trips, drive in dusty or polluted St. Louis conditions, hot or cold weather, or haul heavy loads, you’re driving in severe service conditions. Your Master Auto Repair advisor can help you evaluate which schedule to follow.

So check your sedan owner’s manual or talk with your St. Louis service advisor about where and how you drive. Should you be changing your oil closer to the regular schedule, or the severe service schedule? You need to make the call.

Let me give you an example of this. Some newer sedans have an oil change indicator. It has a sophisticated computer algorithm that tracks number of cold starts, engine temperature, RPMs, mileage, and many more variables to come up with a recommendation for when to change the oil.

Depending on driving conditions, the indicator in one test vehicle came on at anywhere from 2,500 miles to almost 7,000 miles. It’s typically just over 4,000 miles. What this tells us is that sometimes, we’re driving easy miles that are easy on the sedan – like a long road trip. Sometimes, we’re driving hard MO miles – like towing a trailer or a lot of around town driving. But, usually, it’s a combination of both.

Once again, it’s up to you to make the call as to when to change your oil at Master Auto Repair to protect your sedan engine. Another place where MO drivers can go wrong is with the type of oil they use. More and more new cars are coming to St. Louis owners filled with synthetic oil. Without going into a lot of detail right now, let’s just say that synthetic oil lasts longer and is very resistant to oil sludge.

But it also costs quite a bit more, so some St. Louis people are tempted to use conventional oil for their oil changes. Now, it’s always best to use the oil recommended by your manufacturer. Check your owner’s manual see if a conventional oil alternative is allowed.

But getting back to the problem, if your sedan came from the factory with synthetic oil, the recommended oil change interval is for synthetic oil. If you use conventional oil, you can’t use the synthetic interval. You need to shorten it.