Ok my mileage dropped,is it because of 10w30 oil 1998 Bonnev - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Reply
 
 
 
Thread Tools Search this Thread
Old 09-09-2005, 03:56 PM   #1
cvc
Senior Member
Posts like a Turbo
Thread Starter
 
Join Date: Dec 2004
Posts: 303
Thanks: 0
Thanked 0 Times in 0 Posts
cvc is on a distinguished road
Default Ok my mileage dropped,is it because of 10w30 oil 1998 Bonnev

My 98 Bonnie dropped from about 25 mpg to about 23 mpg since I put in 10w30 instead of 5w30. It has 170k miles. Tire pressure is 35 psi recent chg oil,filter,air filter,gas filter, whats up ?
cvc is offline   Reply With Quote
Old 09-09-2005, 05:08 PM   #2
Senior Member
Certified Car Nut
 
Join Date: Jul 2003
Location: Robbinsdale, MN
Posts: 15,408
Thanks: 0
Thanked 0 Times in 0 Posts
MOS95B is on a distinguished road
Default

How many tanks of gas are we talking here? Could be bad gas, natural drop due to dirty engine internals, etc....

I can't see how changing from 10W to 5W would matter....
MOS95B is offline   Reply With Quote
Old 09-09-2005, 05:40 PM   #3
Senior Member
Posts like a Corvette
 
Join Date: Aug 2004
Location: South Bend, IN (hometown) Indianapolis,IN (college)
Posts: 1,598
Thanks: 0
Thanked 0 Times in 0 Posts
ELMACHOGERACHO is on a distinguished road
Default

isnt 10 w 30 recommended anyways?
ELMACHOGERACHO is offline   Reply With Quote
Old 09-09-2005, 05:53 PM   #4
cvc
Senior Member
Posts like a Turbo
Thread Starter
 
Join Date: Dec 2004
Posts: 303
Thanks: 0
Thanked 0 Times in 0 Posts
cvc is on a distinguished road
Default well...

the last 5 or 6 tanks full. A local shop guy said the oil would do it. He said thats why alot of the new Ford trucks recomend 5w20,Ford hadto go to this to get the most mileage.. I always ran 5w30 before but the motor seems quiter with 5w30.. What do you guys see for mileage ?? I do alot of highway too,seems I should be more like 26 mpg
cvc is offline   Reply With Quote
Old 09-09-2005, 07:48 PM   #5
Senior Member
Posts like a Camaro
 
Join Date: Apr 2005
Location: Grand Rapids,MI
Posts: 981
Thanks: 0
Thanked 0 Times in 0 Posts
Masterbm is on a distinguished road
Default

I was using 5w-30 during the winter and then 10w-30 during the other month. When I switch I didn't notice any difference. But a series 2 motor does work differently then a series 1 not sure if those difference would have roll
Masterbm is offline   Reply With Quote
Old 09-09-2005, 10:19 PM   #6
Senior Member
Posts like a Corvette
 
Ol' Timer's Avatar
 
Join Date: Oct 2002
Location: New Jersey - Most of Our Elected Officials Have Not Been Indicted
Posts: 1,483
Thanks: 0
Thanked 0 Times in 0 Posts
Ol' Timer is on a distinguished road
Default Re: well...

Quote:
Originally Posted by cvc
the last 5 or 6 tanks full. A local shop guy said the oil would do it. He said thats why alot of the new Ford trucks recomend 5w20,Ford hadto go to this to get the most mileage.. I always ran 5w30 before but the motor seems quiter with 5w30.. What do you guys see for mileage ?? I do alot of highway too,seems I should be more like 26 mpg
I seriously doubt that your decreased milage was do to the oil change. And although some manufactures(like Ford and Honda) have gone to a 5W-20 oil, it'* mostly becuase of the tighter tolerences in their engines and, yes, they do get mayyyybe 1 mpg increase in mielage over heavier weight oils I know that VW recommends 5W-40 Synthetic Oil in their vehicles. It might be time to change the 02 Sensor and plugs. But give it a few more tankfulls to see if you milage improves.
Ol' Timer is offline   Reply With Quote
Old 09-09-2005, 10:23 PM   #7
DINOSAURUS BOOSTUS

Expert Gearhead
 
BillBoost37's Avatar
 
Join Date: Mar 2005
Location: Enfield, CT
Posts: 41,391
Thanks: 0
Thanked 0 Times in 0 Posts
BillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of light
Default

You should see no performance change from 5w-30w versus 10w-30w.

I would instead start looking at how your car is running and do you get any rotten egg smell when sitting in traffic for a while. The rotten egg smell would lead you to change the O2 sensor before it wipes out the catalytic converter.

The O2 is typically the biggest factor in lost gas mileage.
BillBoost37 is offline   Reply With Quote
Old 09-10-2005, 12:19 AM   #8
Senior Member
Posts like a Northstar
 
Join Date: Jan 2005
Location: Richfield, MN
Posts: 781
Thanks: 0
Thanked 0 Times in 0 Posts
alec_b is on a distinguished road
Default

I agree, i HIGHLY doubt your oil has anything to do with it. I run 10W40 in my car and i get crappy mileage, but that'* the car not the oil . Besides 2 MPG isn't a big deal; slight variances in your driving, road conditions, temperature, etc can have an effect on your mileage. But if it really bothers you you can pop a new O2 sensor in there like was mentioned earlier. For ~ 40 bucks it'* a good investment anyways.
alec_b is offline   Reply With Quote
Old 09-11-2005, 01:23 PM   #9
Senior Member
Certified GM nut
 
Join Date: Feb 2004
Location: CT
Posts: 2,099
Thanks: 0
Thanked 1 Time in 1 Post
SSEBONNE4EVA is on a distinguished road
Default mpg

it shouldn't make a difference in the summer.
Winter I use the 5w-30 cause it gets down right cold in new england, sometimes 0-5 above. Thats when oil will loose you mileage.
SSEBONNE4EVA is offline   Reply With Quote
Old 09-11-2005, 04:34 PM   #10
Senior Member
Posts like a 4 Banger
 
Join Date: Jun 2005
Location: Baltimore, Md.
Posts: 120
Thanks: 0
Thanked 0 Times in 0 Posts
rel3rd is on a distinguished road
Default

I read online that the oil companies would be refining "winter blend" gasoline now, due to the Hurricane, as it is quicker and cheaper to produce. I also know for a fact, that I always get less mileage in all of my vehicles due to this "blended" oxygenated gasoline...I wonder if that'* happening already?
rel3rd is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Oil pressure dropped after switching to 20-50?? CSFiend 1992-1999 7 05-26-2006 06:39 PM
5w30 stead of 10w30? NERV 1992-1999 2 01-28-2006 08:35 PM
traction control & check engine light are on 1995 Bonnev steelman93 1992-1999 4 07-25-2004 11:15 PM
10w30 fantastic88 General GM Chat 12 04-15-2004 02:53 AM
Gas Mileage Suddenly Dropped! HELP! toxictelevision 1992-1999 16 03-18-2003 10:57 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 08:38 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.