My friend recently purchased a mint 91 Caddy Deville. It has 130000 miles; obviously easy, well cared for miles. It is driven mainly in SD and MN, 50/50-city/hwy, with occasional trips to CO, NV, TX, etc. As with most Caddy 4.9L OHV V8's, it has a slight main bearing thump, which has been said harmless. Those that don't like the thump are encouraged to try different oils, possibly even thicker. The thicker oils seem fine, with the exception of putting strain on the distributor drive gear. He is annoyed with the main bearing thump and has used Valvoline All-Climate 5W-30 (dealer), which has allowed the most noise. Currently, it is on the second change of MaxLife 10W-30 5qts + ML 10W-40 1qt. It has helped, but the thump/knock is still present. He was going to switch to Mobil-1 10W-30. After discussion, he is seriously considering M1 Truck&SUV 5W-40(Delvac-1). Or will a combo of M1 10W-30 + 15W-50 be a better choice? Is thicker really better in this application? It calls for 10W-30 preferred, but 5W-30 is recommended for temps <32'F. Maybe a good 5W-30 for the winter and 10W-30 for summer is best? All advice and comments are welcome!
Recommendations for 91 Caddy Deville 4.9
- Thread starter DSteven
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It doesn't use/consume any oil (as opposed to the notorious oil burning Northstar). It had a recent thorough tune-up, gets 89+ octane gas and runs great!
The DeVille is mine. The main bearing thump isn't very bad. I had another 1991 DeVille several years ago that had a worse thump. When the 5w30 was in the car, the thump was very prominent. With the 10w30 and 10w40, it only thumps slightly if the car has idled for a long period and the oil is very warm. As DSteven stated, I am considering either the Mobil 1 5w40 or a mixture of Mobil 1 10w30 abd 15w50. I will be interested to hear recommendations.
The 4.9 has a roller cam.
-Oh, that is good. Well a good 5W-30 whould work well for winter!
I would love to swap in a Northstar but I am affraid that would be more trouble than it's worth.
-That engine is a nightmare, compared to a 4.9.
As far as the distributor gear, not sure what that is about. Nothing is wrong with the good reliable distributor and it will last many more hundreds of thousands of miles.....unlike coil packs which would have been replaced several times by now at a substantial cost.
-Coil packs are just fine, lol. It was said the thick oils put stress on the cam where it meets the distributor drive gear. However, I haven't heard any complaints about problems. This may be of interest:http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=001236
and: http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=002077
-Oh, that is good. Well a good 5W-30 whould work well for winter!
I would love to swap in a Northstar but I am affraid that would be more trouble than it's worth.
-That engine is a nightmare, compared to a 4.9.
As far as the distributor gear, not sure what that is about. Nothing is wrong with the good reliable distributor and it will last many more hundreds of thousands of miles.....unlike coil packs which would have been replaced several times by now at a substantial cost.
-Coil packs are just fine, lol. It was said the thick oils put stress on the cam where it meets the distributor drive gear. However, I haven't heard any complaints about problems. This may be of interest:http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=001236
and: http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=002077
This year used a flat tappet cam (do some searching on the web to confirm). An oil with a high dose of ZDDP (Zinc) would be the best choice. Try a HDEO in a 10w-30 weight if you prefer.
I would love to swap in a Northstar but I am affraid that would be more trouble than it's worth. Would it even fit under the hood of a 1991 DeVille? It would sure be unique if it had a Northstar. As much as the car squats in the rear end with the soft ride suspension when punched, the back bumper would probably hit the ground if it had a Northstar under the hood. LOL Talk about the ultimate sleeper!
As far as the distributor gear, not sure what that is about. Nothing is wrong with the good reliable distributor and it will last many more hundreds of thousands of miles.....unlike coil packs which would have been replaced several times by now at a substantial cost.
As far as the distributor gear, not sure what that is about. Nothing is wrong with the good reliable distributor and it will last many more hundreds of thousands of miles.....unlike coil packs which would have been replaced several times by now at a substantial cost.
The 4.9 has a roller cam.
Funny.
DSteven, you could "tear up a ball bearing". I have had 4 Northstar cars and have never had a moments trouble with the engines and you know how hard I drive. I don't try my hardest to destroy my Northstar engines and then blame them for being weak like someone I know.
Oh yeah. I had the oil changed in the DeVille today. I normally do it myself but I am trying to get ready to move this weekend.
It got a Purolator filter and 5 qts of Mobil 1 5w40 and 1/2 qt of Mobil 1 10w30. The store only had 5 qts of 5w40 or it would have gotten only that.
I have noticed that even after ideling this evening, the main bearing thump doesn't seem to be there. So far, the Mobil 1 Truck & SUV 5w40 seems to be working great. It wasn't really time for an oil change yet but over the next few days we are supposed to have daytime highs of -5 to -10 and overnight lows of -20 to -25. I wanted to have synthetic in the car for the low temps.
It got a Purolator filter and 5 qts of Mobil 1 5w40 and 1/2 qt of Mobil 1 10w30. The store only had 5 qts of 5w40 or it would have gotten only that.
I have noticed that even after ideling this evening, the main bearing thump doesn't seem to be there. So far, the Mobil 1 Truck & SUV 5w40 seems to be working great. It wasn't really time for an oil change yet but over the next few days we are supposed to have daytime highs of -5 to -10 and overnight lows of -20 to -25. I wanted to have synthetic in the car for the low temps.
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