Oil Change Interval

[mickey]

Re: Oil Change Interval

Personally, I wouldn't use "dino" oil in my lawnmower. (Literally. I used Amsoil synthetic in my lawnmower. It's a Honda, too.)

An exception is an aircraft engine running leaded aviation fuel. For some reason, airplane engine manufacturers absolutely forbid the use of full-synthetic oil if you're running leaded fuel. I've never heard a satisfactory and consistent explanation as to WHY they forbid it, though. In fact, Lycoming and Continental forbid full synthetic regardless of fuel type. Most A&P mechanics say that full synthetic oil "slips off" the internal engine parts when the engine sits idle for a long time, as airplane engines tend to do, and allow parts to rust. Other manufacturers say that the synthetic oil doesn't get along with the tetraethyl lead in 100LL aviation fuel.

I don't know who to believe as far as airplanes go, but I'm a big believer in synthetic oils for cars and trucks.

Contrary to popular belief, which is supported by deceptive marketing, oil does not "break down." Think about where the natural stuff comes from. It's "made" thousands of feet underground, where it's been subjected to a billion years of extreme heat, pressure and mechanical stresses. A little old CAR isn't going to hurt it, in normal operation. It is possible to overheat oil to the point that the viscosity "breaks down", but you have to exceed the engine's designed performance parameters. My dad ruined a crankcase of "dino" diesel oil in a Ford diesel pickup while pulling a ridiculously oversized trailer up a steep mountain pass on a hot summer day, but ordinarily that's impossible to do. And synthetic oil is FAR tougher than the dino stuff.

Oil will usually need to be changed for one of two reasons: Particulate contamination (dirt, grit, bits of metal) or chemical contamination (combustion byproducts, antifreeze contamination, etc.)

Motor oils are formulated with additives packages consisting of anti-wear additives, detergents and alkaline chemicals to counteract acidic combustion byproducts. Perhaps the most important issue is fighting acid. "Worn out", acidic motor oil reacts with water from condensation to form damaging "sludge." An oil's capacity to counteract acidic byproducts is described by the oil's "TBN", or "Total Base Number." The higher the TBN, the more acid the oil can neutralize. TBN can range from about 6 or so all the way up to 12 or 13. So-called "extended drain interval" oils SHOULD have a high TBN number, if the manufacturer isn't just blowing smoke.

Spectrographic lab analysis of oil samples can be used to track data on wear metals, TBN, particulates and other parameters. Airplane owners are used to that, but there are a few of us completely anal car owners who do it too. In theory, you can keep an oil in service until the TBN reaches ZERO, since anything above zero means that the oil is still alkaline, and therefore incapable of forming "sludge." Those of us who are complete lunatics will change the oil when the TBN reaches 1/2 to 1/3 of the original value, though there is no real reason to do so.

Since a CNG engine burns fuel so cleanly, there is already very little in the way of sludge-forming byproducts getting into the crankcase. That's what people mean when they say a CNG engine's oil "stays clean for along time." Of course, that has nothing to do with plain old DIRT, which is more a function of operating conditions, quality filters and a good seal around the air filter. Complete lunatics (who shall remain nameless) will run a bead of silicone grease around air filter gaskets to ensure a perfect seal.

You can also, if you're a nutcase who shall remain nameless, install a bypass oil filter in your car or truck. Your stock oil filter is a full-flow design, meaning 100% of the oil goes through the filter on each pass through the oil system. (Unless it gets clogged with crud, in which case a spring-loaded bypass valve opens up to allow unfiltered oil to flow past the filter. Better dirty oil than no oil, after all.) Full-flow filters are important because they will immediately remove large particles that would cause rapid and severe engine damage. But they cannot remove the really tiny stuff because a full-flow filter would have to be the size of a washtub to allow sufficient flow.

That's where a bypass filter comes in. A typical full-flow filter will remove particles down to about 10 microns in size. A good bypass filter will remove particles under ONE micron. Anything below about 2 microns is too tiny to cause abrasive wear, since it will remain completely "submerged" in the oil film between moving engine parts, so by installing a bypass oil filter and using a well-sealed, quality air filter you eliminate virtually ALL abrasive engine wear.

A bypass filter, as the name implies, takes a small percentage of the engine's oil flow (around 5%) and squeezes it gradually through a very fine mesh filter medium. Most bypass filter elements are a cellulose material of some sort, which is also good at absorbing water and other such contaminants, so you get THAT benefit as well. (That's not actually an issue unless you make a lot of short trips in cool weather, or have a coolant leak, though.)

A bypass filter is not a substitute for a full-flow filter, of course. You need both. Your engine's oil pump is easily capable of providing enough "extra" oil to pass through the bypass filter without adversely affecting oil pressure. Extra capacity is built in to allow for gradual wear of the pump, and that "extra" oil flow is usually just wasted directly back into the pan via a relief valve built into the pump body. A bypass filter installation can take a couple of different forms: The stock filter might remain in place while the bypass is installed in a separate bracket, and is fed by installing a tee fitting where the oil pressure sending unit goes. Filtered oil is returned to the engine via a hose and a hollow oil drain plug. Or, as in my '07 Accord, the stock filter is replaced by a spin-on fitting which has supply and return lines attached. Both a bypass filter and an oversized, high quality full-flow filter are screwed into a machined filter block which is attached....somewhere. (Good luck with THAT part. I had to drill and tap my valve cover to attach the bracket. Not fun.)

The practical upshot of all this is that you can, in theory, NEVER drain your oil. Ever. You fill the engine with top quality, "long life" synthetic oil. Then you change the filter elements from time to time. Each time you do that, you're adding a quart or so of make-up oil to replace what you removed with the old filter. That is sufficient to keep the additives package up to snuff. If you're paranoid (like a certain lunatic who shall remain nameless) you back up your maintenance regimen with a periodic oil analysis program. The lab will tell you whether the oil is fit to remain in service or whether it needs to be changed. You can also track wear trends and spot developing problems before they get huge. (Though, in practice, that ain't gonna happen with a Honda!)

If you find that your oil's TBN is dropping lower than you like, you simply change the filters more often until you find an interval that stabilizes the oil's TBN at around 1/3 to 1/2 of the original value. And that's it. No more oil drains, EVER. That's kind of a big deal when your synthetic oil is $8 a quart, believe me.

Right now, the oil in my Accord has been circulating happily for about 35,000 miles. But that's nothing. When I sold a friend my old '99 VW New Beetle TDI the oil had been in the crankcase for over 100,000 miles without a drain. At this point, he's put another 80,000 or so on it. No oil changes. He has souped up the engine into something insane, since he owns a TDI tuning shop and the old Evil Beetle is his guinea pig. That oil is tortured daily. It's inky black, since it's in a diesel, but the bypass filter ensures that none of the particles are large enough to cause wear. Compression is PERFECT on all cylinders. No sign of wear anywhere. You can still see the original machining marks on the cam lobes, in fact.

Bottom line: The 3-month, 3000 mile drain interval "recommended" by Jiffy Lube and the like is a SCAM. Even the relatively generous oil change intervals recommended by most new car owner's manuals are extremely conservative. And a GX is even cleaner still.

I'll have to see how the tests work out, but I expect to change my GX's oil no more than twice a year. I don't want to go through the hell of installing another bypass filter in a Honda, with no underhood room to work with, but with the GX's clean burn I'd probably be wasting my time anyway. If it's supported by oil analysis I might even extend the change interval to a full YEAR, which for me works out to about 35,000 to 40,000 miles. We'll see.

OIL DOES NOT WEAR OUT!

[Curtis]

Re: Oil Change Interval

The 5w-20w is recommended for the GX. The lower viscosity oil reduces friction and improves gas mileage. The advantage of synthetic is that it clings to heat, thereby leaving a film on the cylinder walls and reducing cold start wear.

In my opinion, the lack of carbon in the fuel does more to reduce engine wear than adding synthetic oil. If you want an engine to last 500k-1mill k, do the synthetic. Question is... won't you be ready for a hydrogen car before you hit that mileage?

The only problem I've had with my (5) Honda's is that I get sick of them before I can wear them out. My oldest running Honda is 1972 (3 of the Z600's), and I typically get 400k out of the gas versions. Scares me to think how long my GX may last.

[ajgiorgi]

Re: Oil Change Interval

I changed mine at 10k, but it was not too dirty. I might try 15 k next time and keep an eye on the oil color. Changing to synthetic next time.

[Timon]

Re: Oil Change Interval

I think that was the one for the break-in period. The GX uses a harder to find weight of oil so I'll stick with Honda Oil for mine.

[Green GX]

Re: Oil Change Interval

For the first oil change the maintenance minder in my '07 said change it a 8,295 miles. I got around to it a couple of hundred miles later. I put synthetic oil in it and one of the Fram High Mileage filters on it.

Bill

[freedml]

Re: Oil Change Interval

No, it doesn't break down. It's all about dirt removal.

I let it go 15000 in my GX and had the oil analyzed. It wasn't that dirty, and still met 'new oil' standards for lubrication.

My mechanic has a Honda Element, and he NEVER changes the oil He has a 'toilet paper' aux filter which he changes once a month and adds oil to keep the level up.

[ut_bill]

Re: Oil Change Interval

I have heard many times that oil breaks down. What does that mean? Is there a chemical change in the oil?

[CNGLO]

I'm interested to know how often GX owners change the oil in their vehicles. We all know that the oil companies want us to change it every 3,000 miles. I have read that some people say that every 10,000 miles is sufficient for CNG vehicles. Others say that although the oil is not really dirty at 10,000 miles, it should be changed more often because the oil breaks down. I'm curious to know what your experience is.