Some one once said once you use regular oil that you shouldnt change to synthetic and vice versa..It seems like it does happen now..Was that an old wives tale or was that something you shouldnt do years ago??

 

It is a "wives tale". MAYBE was something you couldn't do back when they were first developing the synthetic. Not anymore. You can go back and forth with no ill effects. Even mix it, no problem.
BTW if you ever decide to run synthetic this is a post from Pikachu that convinced me.
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I have used Mobil synthetics in every vehicle I have owned, except one. The ones that the synthetics never had any internal problems, while the one didn't use synthetic toasted the cam bearings at about 75,000 miles. Could it be sheer coincidence? Sure it could, but I still firmly believe in synthetics.

Here are some real world results with synthetic. The vehicle was a 1998 Kenworth T600, 300" wheelbase, towing a 48'x102" semi-trailer. GVW 80,000, tare wt. 48,500. Engine 3406E Caterpillar, 475 hp. Transmission Fuller Super 10. Rear end ratios 3.55:1. Driving conditions were lower 48 U.S., all weather conditions. I sold the tractor at 600,000 miles and got out of the trucking game. Last I heard, it was still in service with the same carrier.

At approx 350,000 miles I changed this tractor from Shell Rotella T to Mobil Delvac1 synthetic.

On the Rotella it was as follows:
Avg. fuel mileage: 5.9
Oil consumption: 1 gallon per 5000 miles (approx)
Drain interval: 12,500 miles
Drain cost: $150.00 (avg.)

Using Delvac1
Avg fuel mileage: 6.5
Oil consumption: 1 gallon per 10,000 miles (approx)
Analysis interval: 12,500 miles
Drain interval: 100,000 miles, as indicated by analysis trends
Drain cost: $350.00 (avg.)

Using these numbers, here is the benefit:

Fuel cost per 100,000 miles (using price at that time of 1.099/gal):
Rotella: 18,627.12
Delvac1: 16907.69

Savings: 1719.43

Makeup oil:
Rotella: 20 gal @ 9.99 = 199.80
Delvac1: 10 gal @ 24.99 = 249.90

Savings: -50.10

Oil Drains per 100,000 miles:
Rotella: 8 @ 150.00 = 1200.00
Delvac1: 1 @ 350.00 = 350.00, filter change at 50,000: 35.00

Savings: 850.00

Overall savings per 100,000 miles:

$2484.33

If you plug today's fuel price number in there, the savings would be $4021.28.

I realize everyone doesn't drive a class 8 truck, but that was my experience with the synthetic Delvac1.

 

i wont run anything but synthetic anymore. been running synthetic in my 94 superduty that has 595k miles on it. switched my 97 over to it after a lifter siezed, and its in the 2000 f350 also from one end to the other....running amsoil. i see about a 10% mileage gain, and am running bypass filters on all trucks. 94 has over 50k on oil (only reason i changed it was cause an injector oring failed) 25k on the 97 on oil and less than 10k on the f350

 

I too run Amsoil, and the dual by-pass filtration on my '95. Have done so for a few years, and had 60k on the last oil, when I had to change it because of my injector upgrades.
My oil analysis have always came out fine, so I'll continue to run it for a good long time!

I've found the Amsoil filters to be of better quality as well, which is probably why they do a great job of filtering with the filter media they use in them.

I changed to Amsoil synthetic when the truck was close to 40K if that helps.

Dale

 

I agree that synthetic are good. I havent used them yet and want to. What is the average change interval?

 

Where can you get the Amsoil and products. I've got about 130k on the engine now so I want to try and help any way I can. Reg oil is 3k to 5k on service int. What 'bout synth.

 

can keep running it as long as your oil test results come back good. go to amsoil. com and you can get the preferred customer deal and get 20% off. or you can get there number off there and find a local dealer. its like $20 a year but all the stuff you buy in a year you make up for that easily. if your gonna switch motor oil i would definately put the dual bypass setup on your truck to keep filtering all the gunk and crud out. see my other post above with how long ive got on oil on my trucks.