20W50: How wrong was I?

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Feb 4, 2003
Manitoba, Canada
Years back when I thought I was an oil expert, I convinced my buddy to use 20W50 in his car, a Firebird of unknown year and engine. I specified in no uncertain terms that this should be done in summer only. No starting below 50 F. (At that time I thought "Shell Super Plus Artic 0W30" was best for Canadian winters) I cannot recall if it was dead dinosaur or synthetic. Anyway, he took his car into a shop and when he came back they had an engine (he cannot be 100% sure it was his engine) dismantled on a bench, they said it was toast and the likely culprit was 20W50. He was never asked to sign a thingie saying they could do whatever they want, and that got him out of his pickle, but I still think about it some times, and since I have you all to chime in on how wrong I was, I thought I'd ask. On a related note, I used 20W50 in lawn mowers for years. I consider it totally bad to start a mower at under 50 F, and I usually allow them to warm up, anyway. The young man at the mower shop once said that 20W50 was "abusive" and to always, always, use straight 30. Our latest mower says that on the oil cap and on the side of the engine, so fine, but the previous one was a used B&S with 6:1 comp ratio, air cooled. I KNOW you have seen them around. Why would 20W50 be bad? I have a B&S repair manual with a viscocity vs temp guide that shows 20W50 would be the stuff to use! I will try my best to not be too defensive to those that tell me I was wrong, especially on the car.
I'm far from an expert so I can't call you wrong. During the past 16 years I have never used anything heavier than 10w30 in a car or truck and never had a major engine problem. I usually use whatever the manufacturer recommends. My owners' manual for my B&S powered Murray 6hp push mower calls for straight 30 or 10w30 below 40 F so that's what I use.
I would be surprised if a 20W-50 oil ruined an engine. My '96 2.8 Audi engine can be run with viscosites from 5W-30 to 20W-50 (according to the manual). During the cooler season (It doesn't get cold where I am in CA) I use 0W-40 oil, but if it gets hot in the summer, I will use 15W-50 (I have used 5W-50 oil in the past year-round). I'm not comfortable with 0W-40 oil at over 90 degrees ambient temperature.
Rob, Pontiac engines blow up because their connecting rods are heavier than railroad tracks. Except of course unless it was a 403 with the main webbing hollowed out and the crank went out the bottom through the oil pan.
I highly doubt the 20W-50 would have caused engine destruction. It may have caused more wear, but that is about it. And you cant compare the oil recommendation of a B&S lawnmower to a car's engine!!! Clearances are the key, and I would assume it would be larger in a lawnmower than a car.
Well, thousands of cars here in Malaysia use dino 20W-50. It's the factory fill for the national car (derived from Mitsubishi). I haven't heard of a case of engine failure due to the 20W-50. Bear in mind it's hot climate here (86-90 degrees every day)
Its interesting you post that. I actually have a question regarding the current oil placed into my car (95 Honda Civic EX 192k miles). A reputatable garage put a different oil than I'm used to, 20W-50 Amsoil Syn Blend. The car calls for 5W30 in the cooler months and 10W40 in warmer climates I believe. I'm 3000 miles into the oil and do not notice a difference. Any clue why you'd put that in this car. The temps are not even really hot yet, 50-60 for cold starts and max out at 70-80 F during the day. Were stuck in spring in New England. Thanks
I highly doubt one crankcase of dino 20W-50 killed the engine. Most (Castrol) 20W-50 deaths came over a series of crankcases....death by cold starts and black tar. Lots of "experts" thought thicker IS better. Also harper writes:
A reputatable garage put a different oil than I'm used to, 20W-50 Amsoil Syn Blend
Never heard of any 20W-50 synthetic "blend" Amsoil - Amsoil makes 2 20W-50's and they are both 100% synthetic. Are you saying without asking, the shop put in Amsoil 20W-50? Strange. Very strange. Shouldn't be a problem especially if it's the Series 2000, which I run year round (PNW) in the turbo - with zero problems - it has a pretty low pumping point, more like a 10W or 15W.
I apologize I was off, I checked the invoice they used Amalie Pro-synthetic blend. I have never heard of it but never heard of Amsoil before this board either....
Don't worry about your advice, you had all good intentions. There are many "experts" on this board that I question. They are self-proclaimed "experts" because they surf the web quite a bit and come up with some experiment solely based on theory. Then on top of that, they claim the results of these experiments as fact. [Roll Eyes] I personlly would not think that the heavy 20W-50 had nothing to do with the engine failure, most cars in Europe are specs for 40-60 weight oil regardless of weather. To make you feel better, the new BMW M3 requires 10W-60 regardless of what part of the US you live in and what weather you drive in.
It's always safer to error on the heavy side than have an oil too light for your application. This is true for racing and heavy duty pulling. The manufacturers don't expect you to go racing or pull heavy trailers so they only recommend the light ones for fuel economy. BMW however didn't realize all their customers are trying to be like Mario Andretti and spin their motors to the redline constantly resulting in failures. So they upped their viscosity to racing weights. Leo [ June 18, 2003, 01:25 PM: Message edited by: pedaltothemetal ]
I have a toyota cressida with 120,000 using 20w-50 hear in North Carolina. Car runs as new with 250,000 miles on it. Great oil for this area but maybe not for Canada!
using 20W-50 oils are not suitable for some engines. Close tolerances in the engine mean less room for the oil. When the engine expands and the oil to too thick, there is not enough room for the oil. It would not use a 20W-50 unless the engine manf. says to use it. Most all GM engines are not recommended for using 20W50 and my Firebird owners manual says not to use it at all.
Originally posted by oilcanboyd: before i discovered this site i always used to used 20w-50 and a fram oil filter for 100,000 miles in my 94 civic ex. i never had any problems with that motor.
More than 10 years ago, when I ran air-cooled motorcycles, I used only 20w-50 and Straight HD-30. About 6 years ago, when I had an old Ford Bronco in New York, I used only Straight monograde HD-30, occasionally HD-40; cold starting be damned! Stragely, that thing cranked up effortlessly even when entombed in a snowstorm. Today, I drive a Jap import: a Suzuki sidekick. I have been brainwashed into trying 5w-30 Multigrade oil in it. I see no evidence that oil weight makes a difference to car longevity and performance, whether one uses Straight HD-40 or a fancy 0w-30.
Originally posted by JB: Well, thousands of cars here in Malaysia use dino 20W-50. It's the factory fill for the national car (derived from Mitsubishi). I haven't heard of a case of engine failure due to the 20W-50. Bear in mind it's hot climate here (86-90 degrees every day)
Nothing wrong with 20w-50. It is great stuff. But if you are the type who likes to try something different, try Straight weight HD-30. If your car likes 20w-50, there's a good chance it'll love HD-30.
Well, I was wondering if I should try M1 15-20 instead of the 0W-40 I'm currently using. I'm redlining my car all the time, I don't experience any temps below freezing EVER, and I pointed out that I'm not just cruising down the road. However, practically everyone suggested I shouldn't use 15W-50, despite the fact that it stays better in grade and is (probably) more apprpriate under high temperature conditions. I guess for a BMW 10W-60 is acceptable, for my A4 a 15W-50 is not okay. Go figure... [Wink]
20w50 is good stuff. Been using for years.  - Over here 50wts were the only thing you could buy only until recently when the 40wts started appearing. 30wt oils are nearly non-existent here.
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