Synthetic oil

Ok my 1999 Prerunner with the 3.4 ltr has 155000 miles on it. I don't know what the guy before me ran but the past couple oil changes I've been running high mileage conventional oil. I heard that can cause probs after awhile so I'm gonna be switching. My question is I would rather switch to synthetic because it's a better oil but I've heard that can cause leaks like crazy. Any advice? Synthetic change or stick to conventional? I can't afford to reseal the engine if I get a bunch of leaks

 

Not to thread hijack but, I have a somewhat related question on this topic. When switching from conventional to fully synthetic, I hear they don't mix well. Is it necessary to first switch to a partial synthetic before going full synthetic?

 

This is old school conventional 'wisdom'. Maybe this was the case 30 or 40 years ago, but today you wont have a problem. Go full synthetic with no worries.

I use Mobil 1 5w-30 high mileage - get it at Walmart for $24.99 for a 5 gallon jug.

 

If it leaks, cant you just go back to conventional?

Personally, I run Mobil 1 high mileage on my truck with nearly 188K on it and have no issues.

 

That's just what I figured and have seen that same info other places as well.. going full synth next change.

 

If it leaks going back isn't going to help will it? It's removed crud and that's why it's leaking

 

It could just be lighter (synthetic) oil finding its way through gaps that thicker oil wasnt.

 

When Mobil1 first came out, oil leaks in an older vehicle were common because after a while sludge is broken down around main seal area and a leak ensued. This problem was solved with "seal swellers" that were introduced into the formula and these are also common in "High Milage" conventional oils. Mobil1 does market a "High Milage" version of their product as I've seen it at Wally's. I'm a believer in synthetics as they run cooler and give added protection in super cold as well!

 

If it starts leaking, either live with the leak/drip or fix it!

I have always switched my vehicles to synthetic oils/lubes and usually don't have issues. If I did, it was usually from the age of seals and the vehicle sitting unused for a long period of time. I hate leaks, so I always fixed the leak when I could.

 

From what people are saying I guess it would be worth a shot. Just hope I don't get a major leak cause I can't afford a reseal on my engine. Should I use my normal 10w-30 or do I need different for synthetic? I live in Florida where it's usually in the 80s/90s but does get below freezing quite often in winter

 

Synthetic oil is not "lighter" or more slippery than conventional.

5w30 is 5w30.

Synthetic requires fewer viscosity improvers to function as a 5w30 so it better resists breaking down.

 

Go to Bob is the oil guy forums. All of the answers to your questions are there.

 

you can switch to synthetic, not a problem at all.

I know what I'm talking about.

I prefer synthetic, but as long as you change your oil on a regular basis you will be ok either way.

 

I bought my 96 tacoma when it had 60K miles on it. I put Mobile 1 5W-30 in it immediately. I ran Mobile 1 in it for 5 years.


Synthetic oils tend to penetrate further than conventional oils, so you can & may get some leakage/sweating. It just depends.... I've never heard of anyone having a leak that caused 'drips'.

I did experience some 'sweating' / leaking ( no drips). I saw most of the sweating at my oil pan bolts. I went around and tightened the bolts a tad - but I'm not sure that actually did anything or not. I also experienced a loss of 1/2 quart of oil every 5,000 miles. No biggie..... Sometimes, when I'd start the truck up....I'd get a 'lifter tap' until the oil pressure built up. Again, that was minor.

I continued to use Mobile 1....and just kept an eye on things. Sold the truck at 110k miles.

 

I have run Mobil One full synthetic 5w-20 in my 98 SR5. When I bought truck, guy before me used just whatever was sitting in his shop, the first time I drained the oil the Mobil One brought chunks of crap out. Drain hole was spitting globs of broke down conventional sludge. I change every 4500 to 5K and it now runs clean. Smooth as can be, odometer @ 285K clicking right away. Truck idles smoother, performs better, and doesnt leak a drop anywhere (besides outta power steering pump pressure hose but thats a whole different story). I would definitely recommend using full syn product at any stage in a taco's lifetime. I think oil stabilizers (Lucas, etc) are also overkill w synthetic products, although they make a special stabilizer for synthetic oils. You can't ask for better quality out of a product.

 

lots of good posts here.

I agree that the additives are largely a waste of money. Liqui Moly (I have no affiliation with them) makes an additive that contains molybdenum disulfide which is a good product. you have to add it at every oil change if you decide to use in in order to get the benefits, which are increased lubrication. But the "one time" treatment products containing teflon are snake oils as proven by Southwest Research in San Antonio and other labs. And they have been taken to court several times.

I've used synthetic oil in my Chevy truck since I bought it at 137k miles. PO used conventional oil. I now have 308k miles. Engine has never been opened and it runs like a top, and gets very good gas mileage. BTW, I double my drain intervals over conventional oil so that is another benefit. If you decide to extend your drain interval, make sure to use high quality oil filters.

 

I have 155k on my taco.Have used only Castrol GTX. All oils are somewhat synthetic appx. 40 %because you can't run straight crude.

 

I just switched over all the fluids in my truck to synthetic. What an improvement!! More HP. Less vibration. Smoother shifting. I used redline cause I read good things about it on this forum. When I first got the truck I changed all the fluids but I used dino. It never felt right. I'm wondering if the first owner didn't use synthetic too.

 

Slick-50 took DuPont to court when DuPont refused to sell PTFE to them, citing that PTFE was not designed to be used in the oil of an ICE, and Slick-50 was marketing the DuPont product in a manner inconsistent with it's design purpose, and falsely claiming that PTFE would bond to engine parts and provide protection.

Of course, the courts sided with Slick-50, provided they used the term "PTFE" and not the trademarked term "Teflon".
The court decision was that Slick-50 was not harmful to DePont's name, and DuPont had no legal right to restrict the use and marketing of its products as ingredients in other products.

So now we have Turtle Wax using it in their products... of course, marketed as PTFE.

 

Yea, I replied to a similiar thread awhile back. Don't go synthetic. I had a Ranger FX4, a mint machine, oil change every 3-4000 miles. At 160,000 miles I "treated" her special with a synthetic oil change. Sure did clean her crud out. The rear main seal began leaking and everything in the 4.0 began rattling/knocking. The synthetic had gotten the buildup out of all the crevasses and openned all engine clearances . Started having to run high mileage oil. Quickly progressed up in viscosity each oil change until it sounded like she was coming apart everytime she was run. She never came back.