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#201099 - 07/25/06 07:14 PM 15-40 "diesel" oil in gas engines???
fins Offline


Registered: 07/19/06
Posts: 71
Loc: ohio
I have a Dodge truck with the Cummins diesel. I have been using Traveler 15-40 oil that I buy at the local TSC store. I have recently switched to Shell Rotella 15-40.
I have thought about using this in some of our cars, but I have read that the "diesel" oil has too much detergent in it for a gas engine.

In a lot of the post on this form it seems that people are using the 15-40 oil in their gas engines, so I guess it must be OK ??

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#201100 - 07/25/06 07:26 PM Re: 15-40 "diesel" oil in gas engines???
LT4 Vette Offline


Registered: 09/12/04
Posts: 12515
Loc: USA
Diesel oil is fine in a gas car, but its 40 weight might hurt gas mileage in some cars.

I use Diesel oil- Delo 15w40 in my Vette no problem.

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#201101 - 07/25/06 08:23 PM Re: 15-40 "diesel" oil in gas engines???
55Test Offline


Registered: 09/22/04
Posts: 1829
Loc: New Brunswick
I've had people tell me if I put 15w40 'diesel' oil in my engine, it will blow up! [LOL!] I've used 15w40 in every car I've had for the past 7 years, never had one blow up yet.

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#201102 - 07/26/06 09:02 AM Re: 15-40 "diesel" oil in gas engines???
TallPaul Offline


Registered: 10/22/03
Posts: 12915
Loc: By Detroit
Diesel oil is not necessairly fine for a gas engine. Fleet type diesel oil that is dual rated for gasoline and diesel is fine, but regular diesel oil that does not have the gasoline engine rating (e.g., SJ or SL) is bad for gasoline engines.

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#201103 - 07/26/06 09:18 AM Re: 15-40 "diesel" oil in gas engines???
Ray H Offline


Registered: 01/16/03
Posts: 4478
Loc: Southern California
There may be premature catalytic converter failure issues even with those dual-rated fleet oils.

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#201104 - 07/25/06 10:41 PM Re: 15-40 "diesel" oil in gas engines???
Steelers Offline


Registered: 04/09/06
Posts: 297
Loc: Denver CO
You may experience a fuel mileage hit and the engine may feel sluggish. Given the high quality of 20 and 30 weight oils there's really no reason to use a 15w-40 in a non-diesel passenger car. A large, older push rod V8 could benefit from the thicker viscosity, if its consuming oil, and the beefer add pack.

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#201105 - 07/26/06 01:05 AM Re: 15-40 "diesel" oil in gas engines???
mcrn Offline


Registered: 11/30/05
Posts: 2554
Loc: FL
Ray H wouldn't the only way a dual rated fleet oil could cause any cat damage is if it is burning oil?

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#201106 - 07/26/06 02:55 AM Re: 15-40 "diesel" oil in gas engines???
wingdr Offline


Registered: 02/03/06
Posts: 56
Loc: ohio
fins, at first energy we use 15W40 in all the vehicles. Including the new ford rangers and ford vans that call for 5W20. I questioned the supervisor and was told that 5W20 was only recommended for the cafe fleet milage and not to worry about it!! Tim

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#201107 - 07/26/06 03:25 AM Re: 15-40 "diesel" oil in gas engines???
the_oil_dealer Offline


Registered: 09/25/04
Posts: 435
Loc: Toronto
quote:
Originally posted by mcrn:
Ray H wouldn't the only way a dual rated fleet oil could cause any cat damage is if it is burning oil?

Which would lead one to the next logical question of "why is my car chuffing blue smoke non-stop"

Original poster, you should be fine, however you might wanna thin it up a lil bit

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#201108 - 07/27/06 07:32 AM Re: 15-40 "diesel" oil in gas engines???
androbot2084 Offline


Registered: 06/03/06
Posts: 178
Loc: Modesto,CA
15w40 for the mixed fleets is totally old school.
New generation oils like Mobil Delvac 1 5w40 and Amsoil Series 3000 heavy duty diesel oil are perfect for mixed fleets and their viscosities come a lot closer to 5w20 than the old 15w40 formulations.

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#201109 - 07/27/06 07:46 AM Re: 15-40 "diesel" oil in gas engines???
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
Well, at about 4-5X the cost ..I think old school will be around for a long time before everyone ante's up for synth in true mixed fleet usage.

..and .. you really need to qualify something like saying that 5w-40 is closer to a 5w-20 then a 15w-40. You're just going to generate a whole lot of needless posting to prode you to define "how in the heck did you pull that out of a dark place".

I'll preempt you by saying that a 5w-40, being a synth with a much broader VI will be thinner at lower temps compared to 15w-40 making the VAST EXPANSE between 5w-20 marginally less in the grand scale of things WHEN COLD.

It's kinda the difference between being obese and morbidly obese.

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#201110 - 07/27/06 08:36 AM Re: 15-40 "diesel" oil in gas engines???
androbot2084 Offline


Registered: 06/03/06
Posts: 178
Loc: Modesto,CA
A lot of fleets are switching to semi-synthetic oils but they are refusing to go with the thinner oil. For example Shell Rotella makes a synthetic blend 10w40 and 10w30 which is perfect for big rigs and is closer to the viscosities that passenger car OEM's call for. But the fleets still buy the semi-synthetic 15w40 because they do't trust the thinner oils not because they cost more.

For the fleets that can afford full synthetic a 5w30 big rig diesel and gas oil is as close to 5w20 as a heavy duty diesel oil can get without taking a hit on the API specifications.

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#201111 - 07/27/06 08:47 AM Re: 15-40 "diesel" oil in gas engines???
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
Can you tell me the advantage in a fleet environment of a semi-synth 10w-40 and a dino 15w-40? Not necessarily a mixed fleet [Confused]

You're making very broad statements that just aren't true except in a very limited sense. You're really putting out bait ..but we'll tug on your line for a bit.

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#201112 - 07/27/06 08:57 AM Re: 15-40 "diesel" oil in gas engines???
androbot2084 Offline


Registered: 06/03/06
Posts: 178
Loc: Modesto,CA
A synthetic blend 10w40 diesel oil will give a trucker better high and low temperature performance less engine wear and extended drain capability and slightly better fuel economy.

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#201113 - 07/27/06 09:03 AM Re: 15-40 "diesel" oil in gas engines???
androbot2084 Offline


Registered: 06/03/06
Posts: 178
Loc: Modesto,CA
About the catalytic converter it is true that heavy duty diesel oils may contain more zinc dithiophosphate then your car engine oils but if you get a synthetic diesel oil that is less volatile you can save wear on your catalytic converter

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