Which is a heavy oil; 30w or 20-50W?
Also i seem to have increased oil consumption(no leaks) does using a heavier oil might slow this down?

Use your search feature to research oil threads, this has been discussed at nasauem.

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Jerry

2004 SL500 Black 55K Miles
2002 s500 Black 90K Miles
1986 300E Gold 233K Miles
1966 Twin Cessna 320D
1989 Jeep Cherokee 233K Miles
1994 Ford Van E150 399K Miles

30W is a single weight oil (thick) 20W-50 is not as thick. When it's a single weight oil the W stands for weight, I believe. 20W-50, the W is for Winter, as in it viscousity rating at winter temps. The 50 is it's viscousity rating at operating temp.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

I have heard that a car that takes 5w30 and runs 10w40 will perform/consume differently, enough to make a difference. I have no idea. The general rule that most people I have spoken with follow is to use the grade the manufacturer has set for your car. What year and model car do you have? Are you running synthetic?

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1989 300CE Astralsilber/Schwarz
1992 300CE Schwarz/Schwarz

The is no "W" after "30". It's just SAE 30.

Single "weight" SAE grades must fall within a range of viscosities at both 32F and 212F. The higher the number the more viscous the oil.

Dual rated grades such as 20W-50 meet the viscosity requirement of a 20W at 32F and a 50 at 212F. The lower single grades up to 20 are usually rated as 20-20W with 20W having a slightly different viscosity range. There is no "W" prefix for SAE 30 and above.

ALL owner's manuals have recommended oil grades that are based on the ambient temperture range expected during the period the oil will be in the crankcase, so the first place you should refer to when selecting grade is your owner's manual.

There is also lots of good information on motor oil at:

www.api.org

Duke