Comments on: 3,000 Mile Myth & Oil Changes

By: denon

denon — Fri, 05 May 2006 06:11:47 +0000

I agree with Jim – just because your car still runs, doesn’t mean you can get away with running grungy oil through it. People figure as long as it drives, it must be OK.

Modern lubricants are much higher quality, and you can get a lot more miles out of the oil itself, however the filter is still the issue. With synthetics, it’s perfectly acceptable to run them many more miles, but you still want to replace the filter. Also, don’t forget how much oil is in the filter – you’ll want to add ~1/2qt, depending on the size of your filter.

Most people figure it’s not worth the hassle of replacing the filter without doing the oil as well – hence the trend. With excellent care to my vehicles, I’ve never had an engine problem, sans a few worn out belts, and pre-emptively replacing a few plugs. A little TLC goes a very long ways – especially when people are spending such insane amounts of cash on their vehicles these days.

By: Jim Lorenz

Jim Lorenz — Thu, 04 May 2006 21:29:52 +0000

I was an aircraft powerplant mechanic in the air arm of the U.S. Navy during the Korean war. There I learned about magnetic drain plugs. Piston engines rely on cast iron rings to seal the combustion gases, etc. They rub on steel cylinder walls. Both steel and iron are ferritic, thus can be attracted to a magnet. Some of the particles created in an engine are small enough to pass through commercial oil filters, but they can’t pass a magnet that works 24/7.
This is one reason for changing reciprocating engine oil on a tme or mileage basis. You want clean oil in your mill, and you want to see that magnet fairly often.

We never changed a radial engine’s oil because of their (designed) high oil consumption. A four hour flight with an 18 cylinder, 2,800 cubic inch, 2,200 horsepower enigine could consume 4 to 6 gallons of Avlube (about 50-60 SAE Wt.) But the maintenance mechanics could check on the interior health of the engine and the hydraulic systems by checking the magnets in their respective sumps. Even jet engines have magnets in their lube and hydraulic systems to trap & check for particles that shouidn’t be there.

Oil is a lot cheaper than engines. Look for a fine, face-powder textured grey film on your crankcase drainplug magnet. Wipe it off with a paper towel. If you see any large shiny particles listen to your oil pump with a stethoscope, and to your engine over all for unusal noises, or plan to sell the car. If the engine builder says change the oil every NNN miles, do it. What do you know that the designer/builder doesn’t? Again; oil is cheaper than engines.

I’ve driven over half a million miles since I was 14 and have had a dozen or more cars. I’ve only had 3 engine failures: 2 were fiber timing gears and 1 swallowed valve; none of which I could attribute to lubrication failure.

By: Martha

Martha — Tue, 02 May 2006 01:57:29 +0000

I love Car Talk (Tom and Ray are my favorite company on Saturday mornings!!) so i’ll settle on changing my oil every 5k miles

By: jim

jim — Mon, 01 May 2006 19:40:59 +0000

From that it sounds like a 1 yr oil change (if we’re talking 12k miles/yr, not 20k miles) isn’t that far off from being reasonable when using synthetic motor oil.

“TOM: Synthetic oil is also more popular there. And synthetic motor oil only needs to be changed every 10,000 miles, which works out to about once a year for the average German driver.”

By: CK

CK — Mon, 01 May 2006 19:36:13 +0000

A third party opinion; CarTalk

By: jim

jim — Mon, 01 May 2006 19:05:36 +0000

The moment that oil goes through the system, it looks all black and thick with junk, I’m comfortable going the extra 6k.

By: CK

CK — Mon, 01 May 2006 17:50:36 +0000

Personally I think one year/12K miles is a bit of a stretch. While I’m certainly not a 3K mile man I invite you to change your oil at 6K sometime and compare it to new Mobil One. If you feel comfortable with those impurities for another 6K miles go for it but good luck.