Well today I was cleaning my motor and I looked over and saw it said castrol full synthetic written on the side by the battery. I bought the truck used about 6 months ago and havent noticed it once I know I cant believe it either. When I bought the truck the dealership changed the oil which im sure they didnt use full synthetic and I just changed the oil about 500 miles ago and put in castrol but not synthetic. Im kinda freaking out because ive put 5000 miles on it now just running regular oil. I thought I read on here that once you go to synthetic you cant switch back to regular. Is that true? If so should I drain the oil and put synthetic in or will I be fine and run synthetic next time. I was going to switch anyways next oil change. Let me know

Thanks Cody

 

You can switch back and forth from conventional and synthetic oil as many times as you want to, however, synthetic offers a lot more protection and benefits than conventional oil. Because synthetics hold their properties longer, you can basically double your change intervals than when using a conventional oil, so there really is no cost savings going conventional.

I've been using 100% full synthetics for over 20 years now, changed at 6000 miles vs. the 3000 miles I used to change conventional oil at...

 

ok cool thanks for your help hammer. What filter are you running? I have a mopar one right now but couldnt find anything on how many miles its good for.

 

The dealer Mopar ones are made by Champion Labs and are high quality but the Wall Mart Mopar ones are Fram - crap. I like anything made by Champion (K&N, Royal Purple, Mobil 1), Purolator is great too. My personal favorite is Wix which can also be purchased at NAPA as their NAPA Gold...

 

I agree with Hammer. You can infact MIX the 2 oils, which completely disproves the theory of not being able to switch back-forth! They do and will mix together granted you use the same weight oils.
At the end of your conventional oil life, dump 1/2qt of Marvel Mystery oil in and drive about 2-300miles. That will clean up inside nicely prepping you for good Ole Synthetic again. I'd change Synthetic every 5kmi.
Also, Synthetic Blends have only 30% Synthetic and 70% conventional mix. You need Full Synthetic oil to get a 100% Synthetic blend. They do make different base stocks, Group II and IV, but as long as you go Full Synthetic dont really matter because your treating your engine at that point.

 

Sweet thanks for the help. Ill probably just run this oil and then on my next oil change switch back to full synthetic. When you say the Marvel Mystery oil do you mean put it in now or when I do the synthetic?

 

He means put it in about 200 to 300 miles before the next oil change.

 

The gap between conventional and synthetic oil prices has closed so much now, it's an easy call for me, now. A shop might try to nip you a little bit on synthetic vs. conventional, but if you do it yourself, it shouldn't cost you that much more. I like the peace of mind that I can push it a little on synthetic fluids. I try to change every 5k miles but I end up closer to 6k before it actually gets done. That shouldn't be a problem with syn, but squeezing an extra k on conventional is probably not so good. Don't buy the hype on the "super filters" - extra guard, double guard, tough guard, blah blah blah. Just get a standard, quality filter like a WIX or MOPAR (not a Feaux-Par), install it properly, and change it everytime you change oil, and you should be fine.

 

If you ever have a doubt, get on the Blackstone site and request a free sample jar and send it in to be tested at change time. Last I had my oil tested I think it was about $25. Have done it twice with my current truck, once with RP at 6k and once with Valvoline Syntec at 6k and the results were almost identical - and they suggested I could run the oil another 2k miles - so I KNOW 6k is safe in my truck. I do the Valvoline almost all the time now because I can catch a 5 Qt. jug on sale for $28 WITH a free K&N filter at Advance. So I'm looking at roughly $36 for a full change with a great quality filter...

 

RP sent me a oil sample test once and it was a pretty nice kit. They did it because I mentioned it stained the inside of my engine (noticed it when I did the cam swap) but they results they gave back were pretty impressive