[V8] Causes of Bad MPG?

Wed Jan 10 23:34:15 EST 2007

That's what I thought too.  That's the way it used to be.  But oils 
change.  Formulations change.  Porsche denoted Mobil 0W40 for all cars, 
all years, all engines.  Period.  0W40 is what the factory and any 
dealership is putting in.  BMW is now putting in Castrol 5W40 and 
recommends it. 

I'll take their word over anything else.  *shrug*  I don't mean any 
offense to anyone, but I think that their engineers know what's best.  
Are they designed for new bearings?  Maybe.  But I've run that weight 
oil in cars with lots and lots of miles, and never noticed a problem 
___unless there was one there before___.  If you change your oil every 
3000 miles, if the engine is in good operating condition, you shouldn't 
have a problem.  If you lose oil pressure when you run 0W40 but not when 
you run 20W50, you have a problem.  Masking it by putting in heavier oil 
isn't going to fix it.

Again, maybe the wider the spread means the quicker it'll break down.  
But Mobil guarantees its fully synthetic oil well over 10,000 miles.  I 
don't recommend that, I do mine every 3-4 months regardless.  If it's 
good enough for them, it's good enough for me.

~Scott Simmons

quattro + 5 or 8 = fun wrote:

>although the 30 weight hi temp viscosity is essentially the same as the
>multi-weights, it has been proven that multi weights ultimate do not hold up
>as well under heat as straight weights do.  the modifiers that alter the
>cold flow abilities of an oil, tend to break down over time.  from what i
>have read, the bigger the number spread, the less stabile an oil is at high
>temps.  as i understand it, this is why you usually don't find a 0w40 in a
>dino oil.  the dino properties just don't take to the modifiers all that
>well.  However a PAO's (group 4 and 5) synthetic tends to remain much more
>staibile from the get go because of their basic properties...which group 3
>and dino juice does not possess.  like someone said earlier, they were
>concerned about using 5w30 oil in their ford in the summer, i too had the
>same fear.  after considerable research, i came to the conclusion that newer
>alloys used in engines don't need such thick oils to protect the contact
>surfaces.  ultimately, they withstand much better then the older metals did.
>a natural result of using thinner oils in these engines is better economy.
>i personally use Redline in all my german cars.  including my 12 quart
>mercedes.  at 7 bucks a quart, it aint cheap.  but after pulling apart the
>engine on my 4000 and 200 to build up the heads, i am glad i have been.
>they both looked and mic'ed to almost new tolerances.  that is with 300K on
>the 4000 and over 200K on the 20V 200.
>
>lubrication (FOR CARS PEOPLE!!) is a challenging subject.  but, kinda fun to
>learn more about.  read more here:
>
>http://bobistheoilguy.com/
>
>
>Shayne
>
>
>PARTING:  1972 Mercedes Benz 280 SE 4.5
>PARTING:  1986 Audi 4000 CS quattro
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>>From: Scott Simmons <indischrot at gmail.com>
>>Date: Wed, 10 Jan 2007 18:02:30 -0600
>>To: <dsaad at icehouse.net>
>>Cc: <v8 at audifans.com>
>>Subject: Re: [V8] Causes of Bad MPG?
>>
>>A 5W30 weight oil will have the same thickness in the summer as a 10W30,
>>a straight 30, or a 0W30.  They all have the same viscosity at high
>>temperatures.  The difference is that a 5W30 will be thinner at colder
>>temperatures than a 10W30, but thicker than a 0W30.
>>
>>This is why I recommend 0W40.  It has the incredible thinness of a 0
>>weight oil when the car is first started (winter or summer) which allows
>>for quicker oil pickup to those bearings during the first revolutions as
>>well as less of a battery draw.  Ever notice how the engine hates to
>>turn on cold mornings?  Thin the oil and the engine will respond
>>faster.  It also will hold up like any 10W40 or 15W40 at high
>>temperatures.  I've never needed anything thicker than 40 weight (except
>>in a 904...) even in triple digits.  For Arizona-esque climates, a 5W50
>>by Castrol would be a good choice, as those areas might require the 50
>>weight in the summer.
>>
>>While poor oil viscosity choice can cause bad gas mileage, I don't think
>>it would be to the extent that is the case (that started this thread).
>>
>>~Scott Simmons
>>
>>dsaad at icehouse.net wrote:
>>
>>    
>>
>>>As long as you are in the warmer part of the state, I don't see much problem.
>>>I have run Delo 400 15W40 in every car I ever owned and year 'round. It has
>>>been
>>>a problem only a few times in the below zero weather, but that does not
>>>happen
>>>too often now-a-days - what with the global warming and all :-)
>>>
>>>I do have a case of 5W30 oil for my next change though. It is the recommended
>>>oil for the Explorer, and I figured I would try it in the V8 just for fun.
>>>As luck would have it, we are scheduled for a cold snap starting tonight -
>>>and
>>>tonight is when I plan to change it. Should be fun. They are predicting hi
>>>teens
>>>temps with wind chill at -20 in the high country.
>>>I would have a hard time using the 5W30 in the summer though. It just seems
>>>too
>>>light - even though Ford says it is fine. I have never had a oil related
>>>failure
>>>in any motor.
>>>(and that includes the time I tore a hole in my Jeep oil pan while fighting a
>>>giant sagebrush)
>>>
>>>
>>>Dave
>>>
>>> 
>>>
>>>      
>>>
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>>    
>>
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