Topping off due to oil consumption, extend oil change interval?
 

Just a shower thought... I know oil and filters are relatively cheap compared to repairs needed due to neglect...

But if about 1qt is burned off every ~3k miles, and the usual oil change interval is at 7500k, can you delay it by another 2-3k miles as there is "fresher" oil due to topping off?
Assuming the oil being used is full synthetic, and the oil filter is something like a Bosch Distance Plus (which claims protection up to 15k miles).

I use the recommended F series filter bought from Honda and change the oil every season, about every 4-5000Kms. Cheap insurance compared to a $3000 longblock.

You should be fine. Do an oil analysis at the end of a 10K mile interval if you're worried.

I use 10K mile intervals on my 177K mile TSX DD. Its been fine for ages.

Obviously, type of use matters. My S2000(s) are either sitting around or being tracked, with not much other use in between. So I don't use a 10K mile interval.

I would, however, recommend using the factory filter and torquing it to spec (for future posters....you'll never win any argument stating that this filter can be hand tightened). I believe the Honda interval for that filter is 15K miles.

Your old oil is still old. If you have a fish tank and the water is getting dirty, adding a cup of clean water isn't going to improve things. Think of your oil the same way. As long as you change the oil at the recommended intervals for your driving type you'll be fine.

I've always thought of/wondered the same exact thing for a long time (too lazy to post about it though).

I top off every 2k miles (my Ap1 burns 1qt every 1800-2000 miles). Instead of replacing oil & filter every 5k miles, I do it every 7.5k miles (which should be fine I think... regardless if it's old oil).

I go 15k miles on my oil filter(but I do use a large oil filter) 7500 miles on the oil(my '06 doesn't use much oil, less than a qt). If you add oil you do refresh the add pack, oil doesn't wear out the add pack does. Now if the oil shears out of grade(either up or down) 1 qt. will help with that to. If my car used a qt. every 1800 to 2000 miles I would get a UOA at 8k miles and see what it tells me. My bet is it would be good to go more miles even to the point of not having to change the oil(but you still have to change the filter) because you are doing it 1 qt at a time. But a UOA will tell you one way or another if the oil is good for more miles.

I'm in the first 1/3 of our 9k+ miles trip in our S and I just changed the oil(not the filter) so I won't change both till we get home in around 6k to 7k miles from now.

Rod

Technically yes as the TBN reading will be propped up by the fresh oil, so it will have better cleaning properties and be able to neutralize contaminants longer, so yes.

If I recall Slalom44 having 40k mile oil changes but he would use 15-20 quarts between oil changes in between, so he was effectively getting 3-4 oil changes worth of fresh oil during his exceedingly long oil change interval. lol

I agree with Zeroptzero and others. Topping off the oil regularly maintains the additive package of the oil, which maintains the TBN and dispersants. In effect, this allows the oil to work effectively at lubricating wear surfaces and keeping the engine cool without sludging or deposit buildup.

What it doesn't do is remove wear particulates from the oil. Silicon particle ingestion through the air filter is the worst of these. Tiny fine grains of sand accumulate in the oil over time. Our oil filter does a good job of filtering these particulates completely at sizes of around 15 microns and above, and filter most particulates between 10 and 15 microns. With longer oil change intervals the particles in this size range can accumulate. In my opinion particles in this size range are harmless while the engine is running but can cause very slight wear during each cold start, before the oil film thickness (and hydrodynamic lubrication) is established with oil pressure.

This wear is minimal, and would not reduce engine life over the normal life of an engine if you were to extend your oil change intervals to 10K miles, IMO. But I believe that if you're hoping to keep your car for 400,000 miles or more you might have excessive wear in your bearings, rings and cylinder walls, especially if you have lots of cold starts and short trips.

I was wondering when oil burns, how much of tbe suspended contaminants burn with it, and how much gets left behind?

Whatever gets left behind, that doesn't get trapped by filter, will accumulate over time as old oil burns off, and new oil is added in its place.

Also, I don't think filter bypass happens all at once, fully off until on. As the filter media begins to be clogged, bypass begins to happen. Only a little at first, and only under curtain circumstances. But then bypassing more and more often, in higher and higher quantity.

So if you are going to extend your oil change interval because of constant oil burn and new oil added, don't extend your filter change interval too much.

Its ok to change filter only and not the oil.

If the oil gets burnt and pushed out the tail pipe so does everything that the oil had suspended in it. If you run a Wix or Honda air filter you get great filtration, I run my air filter 6 years or when the air filter restriction gauge tells me to change it(so far its been done by years). Put 90k miles on my last a/f and still had no restriction showing on my gauge. You should change the oil filter as one would if you had changed the oil, a oil filter can only hold so much dirt and once its full you go into bypass mode and than no oil gets filtered.

Rod