Most HDEO's are dual rated. AFAIK, The exception is Rotella. The only dual rated Rotella is T6, 5w30 multi-vehicle version.
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Considering the #1 and #3 brands of HDEO in the US are not dual rated, the #1 brand having a large, large percentage of market share in the US, your statement is a stretch.
Rotella and Delvac are not dual rated.
Delo, Guardol ECT/ Super D XA, Citgo 600/700 and Duron are.
Rotella makes up the vast majority of market share in the US. Delo and Delvac fight for #2/#3. (Delvac was 3rd last I heard.) With P66/Kendall #4. Then citgo/Mystik and petro Canada coming in 5th / 6th.
For strictly 15w40.
Dad had a ‘78 Malibu wagon with the 305. Last year or so we had it, it barely started, and when it did it coughed out huge clouds of black smoke. It maybe ran on 5-6 cylinders, and it only stayed running if you revved the heck out of it. Shut it off, and it would ‘run on’ for 2-3 minutes steady.
I remember my dad saying it was ‘carboned up’; looking back on it now it was probably a worn cam issue. Had a neighbour with an Olds Tornado that did the same thing just not as bad.
The 305 Chevrolet V-8 is an absolute garbage engine, second only to the Vega 4-cylinder (and maybe the diesels).
I remember my dad saying it was ‘carboned up’; looking back on it now it was probably a worn cam issue. Had a neighbour with an Olds Tornado that did the same thing just not as bad.
The 305 Chevrolet V-8 is an absolute garbage engine, second only to the Vega 4-cylinder (and maybe the diesels).
Considering it is basically the same design as the 350 Chevy (even same rods and crank - just a smaller bore) and the 350 had the same common poorly hardened camshafts in that 78-83 range, I would say that is a very false statement. All the 300k mile plus 305's out there have proven it's reliability. Your dad's probably did have a camshaft issue as that was right in the short stretch that they were really bad for it ..but it hardly makes it comparable to a vega engine or any of the many other engines made today or back in the day that are unlikely to go 300k miles. And not sure why you're bringing up a toronado with a completely different engine design? They never made any with a 305.
Huh, learned something…thought the early 80’s Tornado came with the 305, but it just had the Oldsmobile 307. Cool.
I though the design of the engine made it prone to more problems - the smaller bore and smaller heads made it more prone to carboning up, so it was a very inferior engine to the 350.
Anyway, yeah, there are some high-mile 305’s, but most did not make it through without problems.
I though the design of the engine made it prone to more problems - the smaller bore and smaller heads made it more prone to carboning up, so it was a very inferior engine to the 350.
Anyway, yeah, there are some high-mile 305’s, but most did not make it through without problems.
Was at WM today and looked at all the Rotella products. Although all the jugs pictured, on the front, a picture of a pickup and semi, looking at the back there was no API certification. 
I had a 305 out of a i think 85 c10 that I had in my Malibu. Ran really strong for a mild combination, 14.3@95 with a 3.08 rear. But it always ate #7 exhaust lifter. Eventually I let one go too long and destroyed Edelbrock cam. I do not recall the original cam having any odd wear but likely was not paying much attention. Motor only had 45~k on it came out of a wrecked truck.
Sold it off and I remember hearing they continued to have #7 lifter issues
Sold it off and I remember hearing they continued to have #7 lifter issues
The smaller bore made it less ideal for upgrading for performance although lots of guys were able to make 300hp out of them with the right upgrades, but it always made sense to go 350 for the extra cubic inches and better bore/stroke ratio. Also they weren't really prone to carbon but they were prone to pinging, the ones I had I usually ran 91 octane because of this plus I usually had the timing over advanced for more power (I was 18-23 when I had my first 305s) and the 85-87 era lg4 engines had 9.3-9.5:1 CR so that made them even more prone to pinging, especially the Canadian models that has no ECM or knock sensor.
Anyway I've seen a lot more 305s with a ton of miles than 350s. Probably because they made a lot more of them through the 80s compared to 350s but they also had less power and rotating mass on the same rods and crank.
My 89 had 332k miles when it got retired. I tried and failed to blow that engine up but I did get exhaust manifolds cherry red.
If I remember correctly they had lousy heads for making power? And with a longer stroke they wouldn't take to high RPM's.
Same stroke just smaller bore. No issues with rpm compared to a 350. Stock heads sucked just like stock 350 heads. They would raise compression when put on a 350 because they were 58cc combustion chamber, but really they were only good to like 250hp without head work. Not sure how I remember any of this stuff as I don't own one anymore and never will again.
Biggest 305 issue in the years I had was bad valve seals (at least in the mid 80s ones). I actually replaced the missing catalytic converter on my 83 just to hide the occasional blue puff on startup. Also they liked to leak a lot compared to the more modern ls engine.
I always heard if you replaced the original cam you'd never have an issue again, but can't confirm as the only one I personally saw fail my dad just drove it that way for years. None of mine ever failed over several hundred thousand combined.
It's possible there was some weird issue with the block on some of them such as the one you had, but it's not something I've heard of before.
Also it seemed like the camshaft problem was rare after 83, and non existent 87+ when the cars all went to roller cam. They used the same engine up to the late 90s with vortex heads and a lot more power.
The narrower bore forced some pretty small valve sizes. 350s had something like a 2.02 and 1.60 valves, but the 305 was limited to something like 1.84 and 1.50. Since the annulus (the valve open area) was a function of radius squared and lift, those smaller valves, and the low lift cams of the time, killed the 305 ability to breathe.
Even a big carb, headers, or higher lift cam, couldn’t overcome those little valves. They couldn’t be any bigger on that narrower bore.
Yeah they were meant to make 150-170hp and get 25mpg, and last a long time. Some magazines made some pretty good power out of them despite the handicaps you are talking about, but the same $ out into a 350 will always make a significant amount of extra power, given the same compression ratio, Cam etc
I took a serious look at upgrading the 5.0 in my 1985 Trans-Am. A 165 hp 305 with a electronic Q jet. There was a 190 “HO” 5.0 that year, with better cam and exhaust.
No real ROI with any of the usual tricks. Tubular exhaust system offered by Edelbrock for that engine/chassis opened it up to about 180, but you just coudn’t get much farther than that, even with the “HO” cam. The Q-jet flowed plenty.
The heads didn’t.
Hot Rod magazine tried upgrading the 305 TPI (a port injected 305) and quickly realized the same thing.
They swapped in a 350.
No real ROI with any of the usual tricks. Tubular exhaust system offered by Edelbrock for that engine/chassis opened it up to about 180, but you just coudn’t get much farther than that, even with the “HO” cam. The Q-jet flowed plenty.
The heads didn’t.
Hot Rod magazine tried upgrading the 305 TPI (a port injected 305) and quickly realized the same thing.
They swapped in a 350.
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That's exactly right, and the valves were more shrouded too, making matters worse, due to the smaller bores.
Yup - i recall people even tried grinding clearance into the decks and it didn't help because you just couldn't flow out of the valve with it roght up against the cylinder, there's a somewhat similar problem with 352 FE's...
I'm sure it just went round, but I don't remember the specifics. It was probably around 1989 or 90. We only had the cam replaced, and I have to imagine there would be all sorts of other damage if the cam actually broke.
My old man had an '84 Cutlass with a 305 that he put about 330k km (about 205k miles) on if I remember correctly and I don't think that engine ever had the valve covers taken off of it.
Pretty sure that vintage Cutlass was a 307 Oldsmobile engine. Different block and heads. Similar power limitation. Good engine for durability.
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