Which oil do you think is better, full synthetic, or other?
Reading a thread in the 7.3 gasser forum got me wondering what most people would choose.

 

whatever the engine manufacturer recommends.
my 2918 explorer uses synthetic. everything else gets regular oil because synthetic finds places to leak out of that regular oil does not.

 

I've been running full synthetic in everything since I bought my 2009 SuperDoody, including the motorcycles and the lawn mower... with no problems. That would be 5 different trucks, V-6, V-8, V-10. The caveat to that would be the 2002 F-150, which always had conventional oil in it since Day 1.

Funny you should say that. The last oil change I did on the 2002, I used full synthetic... and only because I couldn't find Valvoline conventional oil at the O'Riellys I frequent. Guess what...? I'm going to try synthetic blend next time, and maybe it will stop messing the garage floor.

 

I switched over to full synthetic about 25 yrs ago in everything I was running. Have not had major issue with engines since. The outlast what ever it is in.

I switch several older gas engines, mostly heavy seasonal use trucks/equipment. No issues. I’ve heard some have had an issue with major leaks or weeping leaks, I did not. We used to have a few engines that would have seized valves time to time running conventional oil, if they were left to sit for 6 months. Since switching to full synthetic, never had an issue. Those engines are still in service.

Switching to synthetic for winter operations, in cold soaked starts it was night and day. Small auto diesels.

Heavy equipment (graders, dozers, loaders - Cummins, Detroit, etc) I did not switch, I stayed with Rotella T. Most of those are now 40/50 yrs old, and I wouldn’t want to take the chance.

The biggest difference I’ve seen personally was a pair of powerstroke 6.0 diesels torn down in frame. A friends shop was working on them, comparable miles, age, operations, maintenance schedule, etc etc. Internally the conventional oil engine looked like a typical black oily diesel. The Synthetic oil engine looked golden and very clean.

In aviation, some have switched to it, and then switched back to conventional.

Which is better probably depends on the operations and circumstances.

That’s my experience and 2c.

 

Oil today is synthetic. Not even necessary to say full synthetic. if you are using anything else, you are using 1980's technology.

 

there is nothing wrong with 80's technology when driving older than 80's vehicles with a gazillion miles on them.

 

I completely agree. that is what those engines were designed to use. On a modern diesel, it is a short cut with no longevity benefit.

 

my engines WERE NOT designed to run synthetics.
and synthetic oils find places to leak out of where valvoline all fleet 15-40 does not.
my 7.3 diesel will leak around 1 quart per 100 miles synthetic.
my 428 is a little better, only leaking around 1 quart every 500 miles.
put the all fleet in them and they use less than 1 quart over a 3000 mile change interval.

 

With all due respect, you are describing an improperly sealed engine that leaks, and also uses oil, and you are using dino oil that doesn't flow as well as your way of masking and slowing down the leak. Hardly a scientific reason to not use vastly superior lubricating technology.

 

Years of reading, researching, YouTube, and my own personal experience have lead me to believe full synthetics are hands down better in almost every possible way. They flow better when cold, they thin out less when hot, they have better film strength for better wear protection, they evaporate less, they are more uniform so when they do evaporate the components remaining are similar and the viscosity does not change as much, they oxidize less easily, and for all these reasons they last longer. The only reason long drain intervals (15-20k which is ridiculous IMHO) are even possible is full synthetics. You will not see an F1 car without full synthetics. Jet engines are not possible without them.

Leaks can develop during switchover, because conventional oil breaks down and evaporates more readily. This leaves waxes and heavies behind and creates sludge. The oxidized oil contains very small hard particles that work into seals and increase wear in the seals and shafts. The sludge and waxes act like a leak stop. They literally seal up the leaks created by the increased wear. When you put synthetic oil in an old worn engine running conventional oil, the synthetic will begin to break down and dissolve the sludge and waxes that sealed the leak. This is a demonstration that full synthetic base oils actually clean better. Proof that they protect better is that the reverse never happens. Switching to conventional oil will not create leaks in an old engine run on synthetic oil, because the synthetic did not allow for the seal wear nor the sludge and wax to form and seal the wear area. On a modern engine, it’s not that full synthetics are more slippery or thinner or shrank the seals or hardened the seals, and that’s where the leaks come from. The leaks are caused by an inferior oil creating more wear and sludge, followed by a superior oil cleaning the engine better. Leaks don’t always happen during switchover, buts it’s possible late in life.

 

if it is improperly sealed, why does it not leak with regular oil?
your reasoning lacks merit.
my 2018 explorer, which was built and designed to run synthetic gets it. the other do not because it leaks out of them.
regular oil does not. it is not an engine thing, it is an oil thing.

if you want to run synthetic, go ahead.
what i am saying is my experience is synthetic leaks out of the old engines where regulart oil does not.
a little over 193,000 miles on the 78 351M. a little over 189,000 miles on the 79 351M. 52,000 miles on the 289 in the 65 falcon. 94,000 miles on the 428. a little over 496,000 miles on the 88. the 02 diesel is 194,000 miles. the 04 5.4 has 234,000 miles on it. the two that ran synthetic are the 14 6.2 f250, and the 18 explorer.
every time the dealer would put synthetic in any of the older engines, it was back to them on a flatbed within three days with massive oil leaks. they would drain the synthetic out and refill with all fleet 15-40 and the leaks stopped.

 

I have been running shell rotella t6, which is full synthetic, exclusively in mine

 

I've been running synthetic oils in all my vehicles since 1977 when I bought a new 77 Ranchero. I used Delvac 1 (made by Mobil oil) until Mobil 1 came out. As synthetic Trans. oil and gear oils and grease came out I switched to them too. I always found I was getting better gas mileage than other people that were using regular oil. I felt confident that they worked because I used to send samples out to Gulf Checks for analysis at 5K and 10k miles. Right nowe I am trying out Pennzoil Ultra Platinum Plus. It seem to be an improvement in gas mileage over the Mobil 1. (about 1 mile per gal.)

 

In my experience... 64 Falcon, 77 Bronco, 78 Bronco, 86 EXP, 86 Celica, 97 RAV4, 2000 F150 (still own and over 330,000 miles!), 2003 Expexition, etc. Synthetic hasn't leaked out of any of them. Mobil 1, Castrol Syntec, and Walmart synthetic.

Different experiences are interesting for sure.

 

Yes indeed and also interesting is there's no consensus what what constitutes "best".