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I have been using 5W-30 since purchasing my '88 in '94, like it calls out on the oil fill cap. Synthetic for quite a few years now. Just replaced the valve cover gaskets recently due to a crap load of oil leakage, and the top of the heads looked very clean, so something must be working. BTW, it has about 122,000 miles on it, so it's not due to low mileage.
If one were to seldom drive a particular vehicle a 0W-XX(?) might be considered. The W (winter) indicates a lighter viscosity for quick flow characteristics at start up in colder climes in addition for less parasitic drag and slightly better gas mileage. The next number protects from thinning out too much of the viscosity at higher temperatures. One can use different Grades (incorrectly refered to as weight) for the environment as long as the correct Specification is used. So why doesn't a 0W-90 cover all conditions? The grades for differing flow characteristics are established with modifier additives. Those modifiers themselves do nothing for the actual lubricity. A better ratio of oil molecules to modifier molecules lends itself to better lubrication (probably). Everything is a trade off. At least this is my understanding from years of piecing bits of information together from here and there. YMMV.
The "w" grade flows better on cold startup in all climates, not just cold ones. Even at 90F, a 0w-40 flows better on startup than a 10w-40. These days I see no good reasons not to run Mobil 1 0w-40 in an L98 or LT1/4. You'll get better protection at cold start and at high temps and high shear stress. I don't think this was even available when C4s were new, so they couldn't have recommended it.
The "w" grade flows better on cold startup in all climates, not just cold ones. Even at 90F, a 0w-40 flows better on startup than a 10w-40. These days I see no good reasons not to run Mobil 1 0w-40 in an L98 or LT1/4. You'll get better protection at cold start and at high temps and high shear stress. I don't think this was even available when C4s were new, so they couldn't have recommended it.
True. I don't even know why the grade is designated "W - winter". I suppose it is so that those in colder climes understand that initial start up, plus time before oil comes up to temperature, is even more important in colder areas. Of course many of us that track cars know to allow especially single viscosity grade oils to come up to temperature before romping and stomping around the track (or drivers should know, anyway). Bush pilots in Alaska drain their oil at shut down and bring it into heated area to warm it up when flying in way below zero temps, also dilute it with gasoline from time to time if preheat start up won't be available. The gas does evaporate out eventually. Not a good idea for diesel though.
I'm running Shell Rotella T 15/40 because of the high zinc content,1200 ppm. I run it in every car/truck I have, except for the wife's new 4-runner. Been doing it this way for over 30 yrs. She gets the new stuff, I prefer the older vehicles, my newest is a 2001 Dodge diesel and oldest is a 1967 C-10 pickup. I acquired my 89 corvette in July and changed oil immediately after returning home on a 5 hr drive and replaced with Rotella 15/40 and larger filter Wix 51061. The car stays in a garage that rarely gets below 45-50° and once the salt brine hits the roads, it's parked with my classic trucks until a few spring rain storms wash the roads. So far so good, runs smooth and quiet.
The "w" grade flows better on cold startup in all climates, not just cold ones. Even at 90F, a 0w-40 flows better on startup than a 10w-40. These days I see no good reasons not to run Mobil 1 0w-40 in an L98 or LT1/4. You'll get better protection at cold start and at high temps and high shear stress. I don't think this was even available when C4s were new, so they couldn't have recommended it.
I'm running 0-40 Mobil one in my 92 LT1 and I believe it's a great choice particularly in the area where I live where it can be quite cold in the morning but warm up to the 80's by afternoon in spring and fall weather. The superior flow in cold starts is never a bad thing as that is typically when most wear occurs. And, having the extra viscosity at high temps is a win-win in my book.
10w40, 5w30 and it gets bad ring blow-by VC gaskets leak. Has 90k and engine is gunky but not super sludgy. I wanna try a flush on it sometime when I get it out again.
In these oil discussions I never see anyone mention the engineering in the engines for specific OEM oil recommendations.
Modern engines have tighter bearing clearances and run higher oil pressure than a 30+ year old SBC. Lighter viscosity oils are necessary for these tight clearances. A 0W oil in an engine with .002-.0035 clearances at 60psi is not going to support the crank or prevent rod bearings from contacting the crank. In an Ecoboost with .0008 clearances at 90psi it can.
I don't think that's accurate at all. At cold startup - even on a 90F day - the viscosity of a 0w-40 is still waaaaay higher than the viscosity of your straight 30W at 212F (100C). For example, Mobil Special 30 is a straight 30w oil with a viscosity of 10.6 at 100C. In contrast, Mobil 1 0w-40 has a viscosity of 12.9 at 100C, but at 40C (104F, about the hottest cold start you'll ever encounter) its viscosity is 70.8! IOW, there is never a temp where the 0w-40 has less viscosity than the 30w does at its warm operating temp. OTOH, the 30w's cold flow is really poor because its viscosity will be much higher than that of the 0w-40 (they don't publish it on their site for some reason), and your engine is simply unprotected during that extra time it takes for the oil to flow after startup.
The "w" grade flows better on cold startup in all climates, not just cold ones. Even at 90F, a 0w-40 flows better on startup than a 10w-40. These days I see no good reasons not to run Mobil 1 0w-40 in an L98 or LT1/4. You'll get better protection at cold start and at high temps and high shear stress. I don't think this was even available when C4s were new, so they couldn't have recommended it.
I've considered switching to Amsoil's 0w-40 often in my L98. I just never could decide whether it'd be more practical to go 0w-30 instead.
I like the idea of the 0w, though.
In the mean time, I've just been using the M1 5w-30.
I've considered switching to Amsoil's 0w-40 often in my L98. I just never could decide whether it'd be more practical to go 0w-30 instead.
I like the idea of the 0w, though.
In the mean time, I've just been using the M1 5w-30.
I am not sure which to recommend out of those. It kind of depends on the use. When I had my 96 with a 396, I ran the M1 0w-40 because it saw use for street, autocross, and I planned to track it. For street use only with a stock engine, I think the M1 5w-30 High Mileage version would be very good.
This chart (from Tom cfi's coolant temperature thread) disagrees with you. The straight 30 protects better at both ends of the temperature 'bathtub' than 10W30. Over decades of building and maintaining my engines in several applications, I saw differences in bearing wear between 10W30 and straight 30 in the SoCal ambient I typically operate in. "Numbers" and "Specifications" are fine, but empirical results are also valid.
You can disagree all you want. However:
Your original post that I replied to implied that "a 0w" oil won't protect the bearings in a large-clearance, older engine as well as a straight 30w. I pointed out that it's really a 0w-40 being compared (not a straight 20w), and that at cold startup (where the "0w" part of the grade applies), the 0w-40 still has many times higher viscosity than any oil at operating temp. Once both oils are up to temp, the 0w-40 has greater viscosity than the straight 30w and will protect better (all else in the two oils being equal).
My other point is that at cold startup, the 0w-40 will flow much better than a straight 30w and will therefore protect the engine better because it reaches the wear surfaces faster. This is indisputable.
The chart you posted has nothing to do with either of these points. It isn't talking about how fast oils flow to wear surfaces on cold startup. It's also talking about the temperature of the cylinder wall (and coolant) rather than the temperature of the oil. Big difference there.
It also looks like it's 50 years old and comparing a straight-weight dino oil with a multi-vis dyno oil that uses lots of additives to a 10w base to get its multi-viscosity rating. That's ancient history. The good modern synthetics aren't made like that at all, and protect vastly better than any of the oils in that chart.
Watch Richard Holdener's latest video on oil viscosity. He tested several oils using a 5.3 litre LS . It was not surprising at all the results . He started with 5W30 conventional verses 5W30 full synthetic. Not much of a change . He then tested 20W50 full synthetic against 0W10 full synthetic. The lighter weight oil made significantly more power . The 5W30 was not far behind the 0W10 . I think the 5W30 is a good all around choice . Chevrolet called for 10W30 for the 90 - 92 LT5 and changed that to 5W30 for 93-95. Some say the 5W30 is good for older V8's as well .
