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Discussion Starter · #1 ·
My 88 rc has 120,000 miles, the engine runs strong and there doesn't appear to be any leaks. Should I put Amsoil synthetic in it and should I flush the engine first? I have heard that it is not wise to put synthetic oil in high mileage engines!
 

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Do any of your seals leak right now? If so you will have oil all over when the synthetic hits them seals. Synthetics have very small molocules and will have fun following the big old paths that conventional oil has left through the seals. IMHO, it is your money and if that is what you want to do, its fine with me. But, I really don't think that your going to benifet anything with as many miles on your engine as you have.
 

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They now make synthetics with an additive that will swell the seals and stop any small leaks you may have. When I bought my 90 RC, it had around 125K on it. I switched it over to Mobil 1 SuperSyn...the small oil leak I had disappeared, my mileage increased, and and my engine got the protection it deserved. Also, don't worry about flushing your engine before switching over to a synthetic, because the synthetic will break down any deposits and clean your engine out.
 

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Discussion Starter · #4 ·
Ramtuff, So you are saying that you have seen an improvement from conventional oil to Mobil 1 Supersyn?
 

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geronimo said:
Ramtuff, So you are saying that you have seen an improvement from conventional oil to Mobil 1 Supersyn?
I've notice an improvement in every vehicle I've that I switched to synthetic in.
 

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macario said:
Inprovement in what areas?

Mac
I've noticed mileage increases, very slight seat of the pants acceleration increases (keep in mind though, very slight), cooler engine temps, and a cleaner engine. Take an older engine that has a visible sludge build-up in it (visible through the oil fill cap, for example), then run synthetic through it for a few oil changes. You'll noticed the sludge build-up goes away. A clean engine is a happy engine. ;D ;D To help with mileage increases, I like to replace all the other fluids (axles, tranny, t-case) with synthetics too when I can.

BTW, I love the Jake Blues avatar you have. {cool}
 

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The reason I asked the question is because I have tried Mobil 1 and Castrol full synthetic oil on three vehicles: My 76 RC, our 2002 Jeep Liberty, and a 94 Toyota Camry. I logged highway miles, and city miles. I never noticed any measureable increase in gas mileage or performance. My RC has a mech temp gauge and I did not notice a measureable decrease in operating temps either at the gauge or by measuring with a scope at the radiator. My own testing was conducted under varying seasons and for at least two complete oil changes. In my opinion, the cost of synthetic oil does not warrant purchasing it for the above reasons.

Let's look at cleanliness. I've read the literature that assures us that syn oils are cleaner than regular motor oil. I don't know, maybe it is. Again, at around 4 bucks a quart for syn vs about a buck twenty for regular oil, I think I can afford to change the oil a little more often and achieve the same cleanliness of engine.

RamTuff, I don't doubt you have seen differences, but I am just reporting what I have seen on three vehicles. Just my two cents. :)
 

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That's quite alright. I appreciate having your two cents thrown in. Just like you, I'm also making an opinion based on my personal experiences using synthetics. It's interesting that we've seen opposite results.

I like that you brought up the difference in price between syn and dino oils. The cleanliness is my biggest concern, which is the major reason I use syns. I'm sure if you change your oil more often, you can achieve similar results as running a syn longer. I like to change my oil between 3-4K, but there's a lot of time I let it slip to 6K, because I put between 2-3K miles on my truck each month (so you can imagine, time can be limited for me. lol). That right there makes the extra cost worth it to me.

Ok, time for everyone else to chime in. ;D
 

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I used to use "Shell Retella T" oil and added Murrie's oil stabilizer at every oil change. I'd put about 2000-2500 miles on before the oil showed it was getting dirty, and I'd change it at about 3000. I just changed the oil last weekend and I used "Shell Retella Synthetic". I really felt a difference with the "but dino". Regular Retella oil was about $6.29 a gallon a Wal-mart, and the oil additive was about $8 a quart a NAPA. The Retella synthetic was $12 a gallon a Wal-Mart and I don't need to add the oil stabilizor ( or should I say, it's not recamendid to add anything with synthetic ) So in the long run, it was all most cheaper to use the synthetic ( at least for me ) I'll be able to give a better report after a couple thousand miles.
 

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Regular motor oil starts to break down at around 180 degrees or so. So by 3000 miles its pretty well broken down. I think with engines now days if you were to change your oil every 3000 miles with regular oil then there is no reason why it can't last 200K. Synthetic oil can handle 400 degrees or more before it breaks down. Motor oil never gets that hot inside an engine so therefore synthetic never breaks down, but it does get diluted by combustion biproducts. It still needs to be changed because of this, but not as often. I use Synthetic in my Mom's Jeep and in my truck. I change them both at 15K because otherwise i would be changing the oil monthly on them. Neither engine uses any oil in that 15K mile period and no engine problems. I haven't felt a power or fuel mileage change with synthetic. I just do it because i don't have time to change oil all the time.

Still not convinced that you can extend your intervals with synthetic? I'll tell you that a trucking company i worked for changed the oil on thier trucks every 40K and the Cummins engines made it 1 million miles with out any major engine work. They used Kendall synthetic. My boss had a 91 nissan truck that he changed the oil on about every 30-40K miles and used Mobil 1 synthetic. That engine made it about 270K
 

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Discussion Starter · #12 ·
The reason I asked this question initially was because I have an 85 Nissan 4 cyl pickup that has 312,000 miles with no internal engine work. I have been using Valvoline 20-50W Racing conventional oil from the beginning changing oil approx. at 3000 mile intervals. It only uses 1/2 qt. between changes today. I wanted to get some feedback on whether synthetic would be better for my 120,000 mile 88 rc. Your replies have been very helpful! Has anyone used this Valvoline 20-50W Racing oil?
 

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Well - I was talkign with a mechanic of a local racing team, and HE told me that the difference between synthetic and dino oils was really personal preference.

HE also told me that they run Castrol GTX in everything they have... (race cars, trucks, street cars, dragsters... everything) It swayed my opinion towards Castrol... and i gave it a try. Used the 20W-50 in a 1985 R/C with a hair over 115k miles on it (I just got the RC and plan on putting a whole lot more on it, so want to LOVE this truck like my own child)... Since the oil change (2 days ago) i have noticed an EXTREME difference...

Here is what i saw:
1) The engine doesn't have to be primed to start anymore.
2) Idles smoother
3) Accelerates better, with more power and absolutely NO stall from a standstill.
4) Engine temp is down (not sure the segrees) about 1/16-1/8 of the gauge from where it normally sat.

SHe likes the Castrol GTX thick stuff. I have used some synthetics in the past, and not3iced an extreme difference on some cars, and none in others. Honestly, i think it's all about what your car/truck.SUV likes, and what it doesn't.

My CONSTANT advice, though... Stay away from Valvoline.
 

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I use Amsoil. When I replaced all the fluids in my F150 extended cab (engine, tranny, and diff). I noticed a slight increase in gas mileage. My buddy has a single cab with the same motor, tranny, & diff and uses dino oil and I got about 1mpg better. The same weight oil of syn seems to be slicker than the same weight of dino oil. I had a 97 Isuzu that I went to syn oil and it seemed to idle smoother and rev easier. This is just my experience. I use it do to the fact that syn oil doesn't break down and leave as many deposits. Also the oil change intervals that is required of syn oils can make it cheaper, if your worried about cost.
 

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i run 10\30 mobil1 full synth in my 87 cherokee with 218,000 miles. as far as i can tell most if not all my leaks have either slowed or stopped all together. the rear main is shot but it doesn't drip anymore and the air filter isn't all full of oil like with the regular oil. cherokees are known for pumpin oil into the airbox...... i also noticed a small increse in heat control, power and mileage.... not a lot but enough that i can justify the use of it... so its entirely up to you what you want to do.... i run castrol gtx 10\40 in my darts and my 77 PW and it works ok . never had a problem with it.... i switched to the synthetics the first week i had my cherokee. i did an oilchange the 2nd day i had it and 3 days later i was down 4 qts of oil.... i changed it that day to 10\30 full synth and i have NEVER had it that low again... unless mom borrows it and never checks the oil after 4 months:S but thats a different story. so thats all i have to say.. sorry bout the speach!
 

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I run Valvoline synthetic in everything I own. In my 85, my mileage increased from 9 or 10 on the highway at 75 to 12.5 on the highway at 75. Day to day driving nets me about the same, 9 or 10 with conventional, and 11-13 with synthetic.

The reasons they say not to put synthetic in a high mileage engine are as follows.
1. High mileage engines are prone to leaking. Leaking out high dollar oil hurts your pocket, and isn't worth it.
2. High mileage engines that have always run conventional oil will lose all of the deposits that have accumulated in the engine. While some people like a clean engine (me for one), as soon as you clean out those deposits, the character of your engine is going to change. It could start using oil, or just plain leaking it out.

If you want to find out if your engine will benefit from synthetic you can either run a high detergent oil and see if it uses or leaks, or just have synthetic put in.
Wal Mart does full synthetic lube and oil changes for $30. Just make sure you buy a good filter first, don't let them use the fram. I buy a Wix from the local parts house, then take it over there. Considering that we would pay $24 for the oil, an extra $6 is nothing to have someone else change it, lube your chassis, fill your washer fluid, vacuum out your floor and whatever else you do. They do credit you for the oil filter too, like $1...
 

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I've used the Valvoline 20w-50 racing oil in Mopar 340, 360, 383, and 440. I only used it in summer months and switched back to 10w-40 in winter.

Like a few others said, nothing wrong with synthetics at all but on high mileage engines, you could do more harm than good, and also you could leak it out and due to the expense that is probably not what you want to do.

Mac

geronimo said:
The reason I asked this question initially was because I have an 85 Nissan 4 cyl pickup that has 312,000 miles with no internal engine work. I have been using Valvoline 20-50W Racing conventional oil from the beginning changing oil approx. at 3000 mile intervals. It only uses 1/2 qt. between changes today. I wanted to get some feedback on whether synthetic would be better for my 120,000 mile 88 rc. Your replies have been very helpful! Has anyone used this Valvoline 20-50W Racing oil?
 

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Discussion Starter · #19 ·
Macario, What has been your results with the Valvoline 20w-50 Racing formula oil?
 
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