Oil life Rule of Thumb from another forum. Good advice?

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LOL. They are in business to sell new cars after they squeak the purchased ones by the warranty period.
Average age of vehicles on the road is 12 years (in the US). Average miles driven per year is 14k meaning the average vehicle on the road today has over 160,000 miles. Seems to me vehicles do well more than "squeak" by their warranty but you believe whatever you want... 👌
 
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Average age of vehicles on the road is 12 years (in the US). Average miles driven per year is 14k meaning the average vehicle on the road today has over 160,000 miles. Seems to me vehicles do well more than "squeak" by their warranty but you believe whatever you want... 👌
Good Point. I will modify my post...

LOL. They are in business to sell new cars after they get the purchased ones by the warranty period long enough so the owners
won't be run off from purchasing another one of the same make.

Thanks for the input. I feel better.
 

SammyChevelleTypeS3

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I have been following this thread, and think the formula is good, but am wondering if time has a factor in all this. As in my cars that are only driven in summer long trips, but only 1000 or so miles per year. And my daily driver that gets lots of short trips and only a monthly long trip year around but still takes a year and 1/2 to 2 years to get to the miles that the formula figures out too.
Most mechanics will change oil at least once every 12 months regardless of low mileage. I was taught this was to prevent / remove any fuel contamination and moisture that can occur to a vehicle sitting too long unused.
 
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I just changed mine after a year and 5500 miles with 239 hours. Was going to change at 200 hours but life got in the way. Using the fuel formula I come with 6k.
 
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Basically every formula on this thread has me between 8,000-8,900 miles. Recommended oil change intervals from Toyota is 10,000 miles under ideal conditions.
I currently run only 5,000 intervals, but I’m planning on bumping it up a bit.
 
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I am going to go out on a limb and say this is likely very close to the oil life monitor formulas used. Where this might fall on its nose is with hybrids - my Accord hybrid has a crank case capacity of 3.5 qts so it might work there, but IIRC a friend's Prius takes 4.5. I suppose common sense and occasional UOA to confirm is still something.
 
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The concept makes a lot of sense, taking into account highway driving, running the AC, cold starts, idling, and short trips.

Applying it to our 2007 Dodge Grand Caravan 3.3:

Worst case - City driving in extreme cold:

Typical fuel consumption = 20 l/100 km

The engine requires 4.7 l of oil for an oil and filter change.

4.7 l x 200 = 940 l (Sump capacity x 200)

How many km does the van travel to consume 940 l of fuel? 940 l/20 l/100 km = 47 x 100 km = 4700 km

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Best case - Highway driving spring or fall (no AC use):

Estimated fuel consumption = 9.4 l/100 km (This is an estimate - likely close, and chosen to make the math easy.)

4.7 l x 200 = 940 l (Sump capacity x 200)

How many km does the van travel to consume 940 l of fuel? 940 l/9.4 l/100 km = 100 x 100 km = 10,000 km

***********************

And in between?

City/suburban driving in not-extreme conditions would probably result in an OC being required somewhere between 6000 - 8000 km.

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In practice, this won't likely change what I've been doing for years - a pre-winter oil change c. October or November, a spring change c. April, and perhaps a mid-summer change if the mileage warrants it.
 
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The lubricant and engine manufacturers used a formula similar to this for initial baseline when setting the drain intervals in the trucking industry years ago.

Capacity - 40 qt
Fleet MPG - 6.8 mpg
Virgin TBN - 14.5
Fuel Factor (High Sulphur #2 Diesel) - 5

40 x 6.8 x 14.5 x 5 = 19,720

The actual approved interval after testing ended up being around 23,000 mi but the fleet went with 20,000 mi as a more manageable number.
 
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