Used Oil Analysis

You can also hit the forums on BITOG (Bob is the Oil Guy). Lots of owners, some that are on this board, also post there. Pretty much anything you want to know about extended oil change intervals would be there,

As for sampling interval - that is up to you. On the Corolla (1ZZ-FE) - you could probably get away with an oil sample at 10K miles, just to see how much additive package is left (TBN). Some oils do better than others, each car is a little different - so don't be shocked if they tell you the oil is all done by then or if you still have lots to go. If you did this to your Camry - I'd start pulling samples at 5K intervals. They key is to get samples that don't require any top off oil. If your car is consuming oil - you'll have to shorted the UOA interval and see what makeup oil does to the numbers.

When I did mine - I did it every 5K miles - which was just to established my baseline numbers. Did this for oils that I planned to run for the extended oil change. For me - Valvoline Synpower was pretty much gone at 12K miles, Mobil 1 synthetic made it to 14K miles, and Mobil 1 EP made it past the 18K mile mark. Based on that - I could safely run a 7500-10,000 mile OCI with no issue. I still pull UOA once a year to see how the car is wearing in. Also do it if I know there is a big change in the chemistry in the oils (new API class, new oil formulation, etc.)

You can change to synthetic and back to conventional motor oil anytime you want. There is no flush or cleaning phase required - just change the oil like you planned to. On typical oil changes, most of the old oil will drain out, only a small fraction of that old stuff will be left. The additive package in the new oil should buffer it enough that that residual oil will not impact a UOA test. Might be worthwhile to try an oil before you pull the first UOA. I've had experience with some synthetics that sheared up so much, that my overall MPG dropped a sizeable amount.

That oversized filter should work - it is wider than the OEM filter, so you will have to double check that the flange on the bottom of the car is clean and pristine before you go to that filter. Otherwise, it will leak oil.

On my cars - there was significant corrosion on the oil filter flange due to winter salt - so I couldn't use a larger filter without doing some machining first. I ended up using the "tall" filters. Ones that have the identical specification of the OEM filter - just runs 1/2" taller physically. For my application - the extra height of the filter media was enough for me to run my extended oil change interval.

Extended oil change intervals have to done methodically to prevent potential engine damage. Not all engines / situations can do extended oil changes, regardless of how good the synthetic motor is touted to be. Some people baseline their engines very carefully, some pulling samples every 1000 miles to gauge engine oil life. Something I was originally planning to do - but was very cost prohibited in my opinion (case of diminishing returns). So I opted to pull a sample at my usually oil change interval - 5000 miles. If the oil was still OK, I'd left it in there and checked again at 10K miles. From there, I pushed on to see how far it could run. Note that even with the same brand and viscosity of motor oil in the car - sometimes you can run to 15K - 18K miles no problem, next time, it might only hold up for 7K miles. That's why the 5K oil change interval was adopted - long enough to help offset some costs - but short enough that there is a very low risk of any oil related problems.

I could not recommend just running to 10K miles on synthetic without pulling a prior used oil sample - as that is just too risky, especially in engines that have been known to have oil consumption issues. Driving conditions could merit a shorter drain interval - mechanical problem could pop up that could shear down the oil much faster than normal. But it is ultimately your decision to run a shorter UOA or not.

In any case, with Blackstone Labs - they actually wrote up their take on the oil life. So if you pull the oil sample at say 5K miles, they'll tell you what they think the oil can do and when to sample next. Terry Dyson at Dyson Analysis also gives you his take, being an independent UOA consultant, some owners value his interpretation more - as such, his tests also cost more than Blackstone.

If you only drive a relatively short distance. say 10K-12K miles a year - best to stick with 5K -6K oil change interval. Even with synthetic - they recommend two oil changes a year, every six months or whatever your oil change interval is - whichever is first.

TAN and TBN - Total Acid Number and Total Base Number = they are metrics for determining how much reserve life the oil has.

TAN finds out how many acidic components are left in the oil, not a measure of acidity. As oil ages and subjected to high temperatures, this number increases. This becomes problematic when the car "sits" as moisture will be drawn in and then form acids that will slowly eat away at internal engine parts. This moisture is generally cooked off during normal operations, but cases of very short duration driving or infrequent driving - can lead to potential engine damage.

TBN is the metric that keeps TAN in check. This is the reserve alkalinity in the motor oil - these base compounds help neutralize acids that form during the normal combustion process. How much of this reserve alkalinity is left determines overall oil "life". As this buffering component is exhausted, the TBN will drop. At a certain point, the oil will be used up - no more reserve alkalinity - meaning it will no longer be able to neutralize those acids and engine damage will occur.

That's why they want you to change the oil twice a year, even if it is a very short interval, as acid components are constantly being added to the engine oil, but there is only a finite amount of reserve alkalinity. Most of the oils designed for extended oil changes have a very stout additive package that includes a whopping amount of reserve alkalinity (TBN).

Correct, even if the oil change interval can cover that distance, its the time that the oil sits in the engine that is also of concern. If you only drove 5K miles a year, I'd still recommend changing the oil twice a year.

Given your driving distance - might even be able to run conventional motor oil at a 6K or 7K interval. No need to stretch to synthetic. Same way - need to baseline the engine and motor oil - oil quality has improved tremendously over the past several years.

If you spent the time and money to pull TAN and TBN numbers periodically through the year - your might be able to get away with only a single oil change per year. They key is how stable the TAN is and how much TBN you have left. If there is plenty of TBN left and TAN is trending pretty flat - that means the engine isn't generating a lot of acidic components and moisture being pulled in. Then you can change it once a year.

This is one of those things you don't want to guess at. Every case is different - one owner may get away with only one change a year, another may need 4 changes a year. Depends on the driving conditions, how the car is driven, ambient temperatures and conditions, condition of the engine, etc.

That synthetics makes a car last longer is still up to debate. Oil change interval and proper filtration likely have more profound effects on engine health than type of oil used. My 1996 Camry has almost 400K miles on the original engine - that one ran exclusively on Valvoline All-Climate conventional motor oil with conventional filters.

Don't get me wrong - synthetics are great fluids to use, but don't think that just switching to synthetics will lengthen the life of the car. Especially when you are thinking of extending the oil change interval - do it wrong with a synthetic (wrong oil change interval, improper filtration), and you may even shorten the life of the engine.

Yes, they still make it, they just updated the name - Valvoline All-Climate is now Valvoline Premium Conventional. Lots of decent conventional motor oil out there Castrol GTX, Havoline, Mobil Super, Quaker State, Pennzoil, etc. As for filters - I used whatever was on sale - but the majority of the filters were Toyota OEM. Bought them in case packs whenever they went on sale - sometimes you can get them for around $3-$3.50 per filter, case is usually 10 filters. If I ran out - I'd pickup a Purolator, K&N, or Mobil oil filter. Used to be a avid Fram filter guy - but after a couple off bad experiences, haven't gone back to them since. I still buy and use their larger PH8A filters - sort of the "standard" filter that lots of older domestic muscle cars use and specialty applications, but unfortunately, no fitment for imports unless you add a remote filter setup.

As I mentioned before - usually not the oil you run, but the regular maintenance that will make the car's last as long as they can. As for the 3K miles / 3 month change interval - that is up to the driving conditions of the car, how it responds to the oil, what's its wear levels look like, etc. There is no single, all encompassing answer to this - each car is unique and will require an oil and oil change interval to meet its requirement.

If I'll hit 400K on my Corolla - I only hope to hit that much, but given a timing chain design and spotty history - I'd be happy with 200K-250K miles on the Corolla (at 215K now). That Camry had the bullet-proof S-series engine (2.2L 5S-FE) and available E-series manual transaxle. The weak point on that Camry is the transaxle - if that holds up + body - 1/2 million miles is nothing.