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Old 07-31-2005, 10:22 PM
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by H3Lady:
I have a supplement advertisement from GM for the H3 and on the cover is says.

quote

20 MPG hwy"

OH I used Quaker state pure synthetic extreme too, as my first oil change. Super reviews for HWY suv useage </div></BLOCKQUOTE>

Most likely there is an asterisk with a statement that clearly states, "estimate." Or, another disclaimer.
In addition, the engine will get better mileage as it breaks in. Also, the use of synthetic fuel will not show an increase in fuel mileage. The weight of the oil affects fuel mileage. Almost all oils, with the second number, under 30W are considered fuel efficient in this day-and-age. The first number is more important for cold engine start ups. Lower numbers get the oil to the top of the engine faster.
That is one reason why using 10w-30 versus 5W-30 in the summer, will not affect overall fuel mileage. The top number is effective after a set engine temp.
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