Using Out-of-Spec Oil for Temp Engine Flush

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My high mileage Toyota Tundra 4.7L V8 uses 5W-20. I recently acquired a case of Lucas full synthetic oil 20W-50 at $1/qt. Various people have advised me not to use it in the truck because of its viscosity. I have been thinking of flushing the engine with either kerosene or SeaFoam per instructions I have found on this site. What I would like to know is this: Can I use the 20W-50 oil with an additive for a short period (5-15 min) at idle without harming the engine? I know that engine flushing is controversial. I am leaning toward flushing with a mixture of oil and kerosene (ratio TBD.) But rather than buy some cheap 5W-30 oil, I would prefer to use this ultra cheap but thick oil instead. I can't imagine why it would be a problem to use 20W-50 for such as short period, but I could be wrong. Also, would it be risky to use 20W-50 instead of 5W-20 during the hot summer months? Your comments are appreciated. Please no anti-flush flaming.
 
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I dunno, but I look forward to the answer as I have just scooped up 8 qt of M1 15-50EP and my cars call for either 5W-20 (Honda V6) or 10W-30 (Chrysler 3.5L).
 
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You're going to get mostly negative responses on the 20w-50. I would run it in the summer for a flush if you already have it but I wouldn't go out of my way to buy it. I highly doubt it will hurt a thing. I don't think the kerosene is a good idea at all. If you're going to use it anyway, the 20w-50 is probably a good idea since it will be thinned out a lot. Or put another way I would be scared to death to run kerosene in a 20wt. Every post after this will be recommending AutoRX instead of kerosene or Seafoam which I agree with.
 
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 Originally Posted By: Throckmorton
I dunno, but I look forward to the answer as I have just scooped up 8 qt of M1 15-50EP and my cars call for either 5W-20 (Honda V6) or 10W-30 (Chrysler 3.5L).
Keep us informed, especially if it goes in the Honda. I'm very curious seeing how my TL responded favorably to the straight 30wt.
 

JHZR2

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 Originally Posted By: BuickGN
You're going to get mostly negative responses on the 20w-50.
\ On the kerosine, maybe, on the 20w-50, for a flush and a very short-term use, I'd not be worried. I'd probably put in the 20w-50, and substitute one of the quarts for a qt. of MMO though, now that I think of it...
 
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 Originally Posted By: Steve S
Why do you want to flush the engine.
Yes, what makes you think the engine needs to be flushed? High mileage alone is not reason enough, are you seeing other things that make you want to clean the engine?
 

Arbuckle

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 Originally Posted By: hate2work
 Originally Posted By: Steve S
Why do you want to flush the engine.
Yes, what makes you think the engine needs to be flushed? High mileage alone is not reason enough, are you seeing other things that make you want to clean the engine?
I am bored and want to fiddle around with the truck while the weather is good. I have done it in the past with other high mileage vehicles and as far as I can tell it caused no adverse reactions. (But who can really tell) I am talking about the kerosene/oil mix being in there for a maximum of 5 minutes at idle...
 
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Nothing risky about it. I'd also guess that this synthetic 20W-50 is thinner at start up now during the hot months than the 5W-20 you were using before was at start up during the winter months. It's all relative, and no damage will occur from using this oil.
 
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The 20W-50 with a quart of MMO substituted in for one of the quarts of oil. Certainly run longer than a 5 minute idle flush. A good highway trip or something. Or use the 20W-50 with a can of engine flush for the 5-15 minutes at 1500 rpm for a quick cleanup. To do more thorough cleaning to the rings/pistons and other critical areas inside, look into Auto-Rx, but not with the 20W-50. They have a website, too with some good info. I have had best results with the Auto-Rx.
 

FZ1

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Forget the kerosene,take the 20-50 back and exchange it for some PP in 5-20. The PP will do some cleaning and won't break your crank when you start it.
 
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I don't see the 20W-50 doing any harm, I used it in a GM 3.8L for one OCI, then went back to 10W-30 with no harm done (I thought it was using oil until I found an oil cooler line leak).
 
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For one OCI I don't see the 20W50 hurting anything especially in the summer. How about giving MMO a shot? Use it in place of 1 qt of the 20W50 oil and run it for 500-1000 miles. Then drain and fill with the suggested oil viscosity. YMMV
 
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 Originally Posted By: aquariuscsm
20W50 is absolutely HARMLESS! Don`t they run something like 40W70 in Australia?
No, it's engine death in a bottle...lol. There was a time when most people ran a thick oil and thought a 20wt would kill the engine in short order. Now that most are running a thin oil they think thick oil is the devil. Get over it guys, practically nothing has changed mechanically and a 20w-50 is not going to "break the crank". How's that Pennzoil doing compared to the RP, any noticable changes?
 
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 Originally Posted By: BuickGN
 Originally Posted By: aquariuscsm
20W50 is absolutely HARMLESS! Don`t they run something like 40W70 in Australia?
No, it's engine death in a bottle...lol. There was a time when most people ran a thick oil and thought a 20wt would kill the engine in short order. Now that most are running a thin oil they think thick oil is the devil. Get over it guys, practically nothing has changed mechanically and a 20w-50 is not going to "break the crank". How's that Pennzoil doing compared to the RP, any noticable changes?
20W50 ftw!!!!!!!
 
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Wait. By "flush" do you mean 10 minutes at idle (w/o load) or do you mean driving on it? Flushing is fine, a thick oil might be the ticket since your solvent of choice, kero will thin the oil a lot. How about this. Add the kero to the old oil when the engine is hot and let it idle 10 min. Drain and fill with just the 20w-50 and a fresh filter. Drive it however long you want and then go back to your normal oil. btw-Biodiesel is supposed to be the best quick flush.
 
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Me,personally,I`d never ever ever ever put anything but oil in my engine. No cleaners,additives,no [censored],no nothing.........but motor oil. Just do religious oil changes and she`ll clean right up!
 
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I guess I've never heard of someone doing an engine flush just because he was bored I was just reading on another forum where BMW recommends using a complete fill of ATF fluid, run at idle for 10 minutes or so, to clean a dirty engine. That would be interesting to try
 
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