[Mike]

I’m not an expert by no means on which is better. Just to put that out there first. Everything I say is just based on personal findings and opinions.

I personally do oil sampling on oil changes. One main reason is I Owen a trucking company and when your dealing with a $35000+ engine you kind of want to know what works best and they will also tell you when you have a potential problem coming into the mix.

I started this with a Cummins ISX engine. Yes it’s a big truck engine but the principal is the same as a gas engine. $35000 motor or a $3500 motor. I bought the truck with 507k on the motor. It had conventional oil in it from the eh day it was new to when I bought it. I drove the truck to 600k and changed it to synthetic oil. Now mind you a truck interval for oil changes veries. I go about 15k miles on conventional and I have gone to 115k on synthetic oil. Ok wait I’m not nuts. Yes I said 115k . The reason why I was able to go that distance on the oil was because I installed a bypass oil filter system and with that system I sampled my oil every 10k to 15k. I sent the oil to Polaris Labs for oil analysis. The synthetic oil tends to have a better additive package in it. One of the big things with any oil is the base number or what’s called the TBN (total Base Number) the TBN is the additives that are able to nutralise the acids that are developed from combustion.
The lower the base number gets in a sample means that the oils additive package is starting to degrade. When doing maintenance on the oil during this time you do change oil filters and what not. Even the bypass filter gets changed about every 40k (huge filter). So as you change filters and sample you do need to put in makeup oil. During the 110k oil change interval I used approximately 40 gallons of oil. Yah it sounds like a lot but the sump on that engine was 11 gallons and both the oil filter and bypass filter combine used 2 gallons alone. I presonally used Amsoil 15w40 high TBN oil. Worked great excellent oil samples until about the 75k mark. My samples started showing that the additives we’re starting to degrade faster and the makeup oil wasn’t able to boost the additives as much. So the next 35k worth of miles it started getting worse. So I changed the oil.
The really cool part of the oil samples is it actually caught a problem before it actually became a huge expensive problem out on the road. I ended up showing high partical levels of iron in the oil. I ended up having a cam roller the cracked and actually cut into the cam. $12000 later it was fixed.
Ok now your going to say that the oil was old. Wrong the base oil really never gets old or wear out. The additives do or well deplete. Base stock is base stock for oil. I put a new cam shafts in and new roller rockers at about 105k. I put on new filters and ran that oil for 5k more or the 110k mark and dumped it. Just wanted to wash out any crap that may have dropped into oil pan. Now mind you at that point I was leaking about another gallon of oil in 15k interval plus the 2 gallons towards that mark. So I decided to change the oil to conventional. So conventional I switched to Cenex 15w40 oil. I think I was paying about $11.00 a gallon at that time. I was running that oil up to 40k on a change. Part of the reason is the oil additives tended to deplete quicker in a conventional but while sampling the samples would come back with normal TBN numbers. Around the 4 mark. I was able to run that motor until I sold it at 970k. At that mark though the oil was good the oil seals and gaskets are getting really hard and stiff and I was getting lots of leaks. Looked like an old Harley after a five Mile ride. It left it’s marks. Lol
I don’t condone running oil that long or short but the fact I was taking the steps with oil sampling to make sure bad stuff wasn’t happening.
Oh by the way. A full sample analyst costs about $32.00 so it’s the price of an oil change for a car now days.
Oil is oil, some oils have a little more parifin in them than others but it still all comes from the ground. Oh and some oils do better in some engines than others because combustion gasses can naturally be higher in one make of manufacturer from another. Just my two cents

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