Proper Oil Change Intervals

My 2005 Lincoln Town-Car book says to change the oil at 5000 miles, which I do. I use a synthetic blend oil. When I reach 5000 miles, the oil minder says the oil is 50% used. Am I changing the oil too much??? The car gets 90% of it’s mileage cruising on the interstate highweays. Very little city driving is done.

What good is an oil minder if the book says change the oil every 5K miles?

I’d go by the book.

In this case the computer is close to the truth. Your type of driving (very easy on oil)is similar to limousine service, and those guys change oil at 10,000 miles.

However, I would go by the book and change very 5000 miles, but don’t worry if you are forgetful and do it 1000 miles or so later. Oil additives have a good safety margin built in.

My wifes Sonata is driven the same way, mostly highway.

Oil analysis tells me that 7500 mile oil changes are not a problem.

What you can do is drive 7500 miles & have the oil analyzed & when the results come back “oil suitable for continued use” you can safely extend drains to 7500 miles.

The oil analysis is a one time cost of about 20 bucks.

You would likely be OK with the oil minder, but frankly I would go by the book.

After reading some of the answers…I am assuming the computer operated oil minder is dumber than the printed manual, regardless and forgetting that the oil minder monitors how many revs your engine does, how many hours it is driven, how much time it idles and so on and so on…but lets be real smart and just always change it at 3,000 miles…come on …wake up!!!

What is the reasoning behind 3000 mile oil changes?

I’m curious why we shouldn’t follow the longer intervals defined by the engineers who design the engines.

Update: Or why shouldn’t we follow the intervals defined in the owner’s manuals which have proven they support several hundred thousands of miles of engine life?

I remember a proposal in congress to increase the recommended oil change interval, the only purpose being to save oil, I don’t believe it passed, but it may not be the engineers decision.

I don’t think that one ever saw the light of day.

Why 3,000 miles. While may father’s 1949 Chevy might of needed 3,000 mile oil changes, today’s modern cars just don’t need that under anything close to normal driving conditions.

Why not just go with the manufacturer’s recommendations? We very seldom see anyone with an oil related wear or damage problem with a car when they follow the change recommendations. Worn out engines were not that all uncommon when I was a kid, but today, very few cars wear out an engine, it gets damaged due to no oil or a broken timing belt etc.

Joseph is right; modern engines run a lot cleaner than your dad’s 1949 Chevy for these reasons:

  1. Electronic ignition and much better spark plugs result in very little misfiring

  2. Electronic fuel injection wastes very little gas and very little raw gas washing the oil off the cylinder walls.

  3. Vastly better oils and oil filters with better viscosity stability and range, more and better additives, etc.

  4. Better piston rings with better oil control with very little blowby to contaminate the oil; my 2007 Toyota uses no oil between changes at 5000 miles. Even the best US engines in 1949 (Cadillac, Olds Rocket V8)would use at least 1 quart (of the poor single grade oil of that era) every 1000-1500 miles.

As a result the normal oil change interval has been stretched over the years, but very severe driving, short trips in very cold weather, outside parking STILL require frequent oil changes due to the condensation and raw gas that forms in the oil pan. No technology changes can cope with that!

Yea, sure, lets change our oil every 3000 miles. By the time the car has 300,000 miles on it, it will have its oil changed 100 times at about $40 per change, that’s about $4000 of oil changes, and for what?, your engine lasts 300,050 miles instead of only 300,000?

You forgot unleaded gasoline. Unleaded gasoline is more responsible for extended oil change intervals than the other items noted with the exception of good oil filters.

You are right! I forgot an important contributor to oil contamination. The unleaded gas and electronic ignition allowed tuneups to be stretched to 25,000 miles. With that came cleaner combustion chambers, less deposits, etc.

I would go full synthetic and go by the oil minder. I drive a SLS which requires synthetic oil (8 quarts). However, the computer monitors my driving and normally recommeds a oil change between 10 to 12,000 miles which I follow. Prior to this car I drove a 93 STS which I bought new and used synthetic oil since day one. I changed the oil every 6,000 and the car had 253,000 miles on it when I sold it with no engine problems.

The economics work something like this:

In stop and go driving changing oil every 6000 miles and using standard dino oil, I would pay $35 max per change, and over 300,000 miles (IF the engine went that far) would spend 300,000/6000X$35= $1750 on oil changes.

Changing oil every 3000 miles would cost twice that, or $3500 over the life of the engine, which would likely be 400,000+ miles with proper coolant changes.

I have seen very few engines, other than fleet cars and taxis, that reached 250,000 miles with the 6000 mile oil changes. We are talking about 15-20 years of ownership.

If you trade cars every 3-4 years, you will not have too many problems, unless you own a sludge-prone engine and live in a cold region.

If you want the engine to last its normal life expectancy a 3000 miles interval for city and 5000 miles for country driving will only cost you $1750 maximum extra over 17-20 years, or about $100 per year.

By “saving” $1750 with the long drainage, you have a more that 60% chance that you will need a replacement engine, during your years of ownership, at about $3500 in today’s money, or a risk-rated cost of 0.60x$3500=$2100. That’s the best scenario.

So changing oil more frequently gets you at least an extra 150,000 miles or more without internal engine work, not 50 miles as you guessed!!.

Agree that if you are a tavelling salesman and drive all day, you can go up to 10,000 miles on good oil in the summer. Those are exceptions to the rule.

I normally keep a car until it either becomes unsafe to drive, fails emission tests, or the major components (engine transmission) need replacing. Since 1964 I have never had to overhaul or replace an engine and only spent $185 on transmission REPAIRS.