Subject: TOP TIER Detergent Gasoline (Deposits, Fuel Economy, No Start, Power, Performance,
Stall Concerns) - U.S. Only

Models: 2007 and Prior GM Passenger Cars and Trucks (including Saturn) (U.S. Only)

A new class of fuel called TOP TIER Detergent Gasoline is appearing at retail stations of some fuel marketers. This gasoline meets detergency standards developed by four automotive companies. All vehicles will benefit from using TOP TIER Detergent Gasoline over gasoline containing the "Lowest Additive Concentration" set by the EPA.

Those vehicles that have experienced deposit related concerns may especially benefit from the use of TOP TIER Detergent Gasoline.

Gasoline Brands That Currently Meet TOP TIER Detergent Gasoline Standards
As of November 15, 2006, all grades of the following gasoline brands meet the TOP TIER Detergent Gasoline Standards:
• Chevron
• QuikTrip
• Conoco
• Phillips 66
• 76
• Shell
• Entec Stations located in the greater Montgomery, Alabama area.
• MFA Oil Company located throughout Missouri.
• Kwik Trip, Inc. in Minnesota and Wisconsin andKwik Star convenience stores in Iowa.
• The Somerset Refinery, Inc. at Somerset Oil stations in Kentucky.
• Aloha Petroleum
• Tri-Par Oil Company
• Texaco

What is TOP TIER Detergent Gasoline?
TOP TIER Detergent Gasoline is a new class of gasoline with enhanced detergency. It meets new, voluntary deposit control standards developed by four automotive companies that exceed the detergent requirements imposed by the EPA.

Where Can TOP TIER Detergent Gasoline Be Purchased?
The TOP TIER program began on May 3, 2004. Some fuel marketers have already joined and have introduced TOP TIER Detergent Gasoline. This is a voluntary program and not all fuel marketers will offer this product. Once fuel marketers make public announcements, they will appear on a list of brands that meet the TOP TIER standards.

Where Can I find the Latest Information on TOP TIER Fuel and Retailers?
On the web, please visit www.toptiergas.com for additional information and updated retailer lists.

Who developed TOP TIER Detergent Gasoline standards?
TOP TIER Detergent Gasoline standards were developed by four automotive companies: BMW, General Motors, Honda and Toyota.

Why was TOP TIER Detergent Gasoline developed?
TOP TIER Detergent Gasoline was developed to increase the level of detergent additive in gasoline. The EPA requires that all gasoline sold in the U.S. contain a detergent additive. However, the requirement is minimal and in many cases, is not sufficient to keep engines clean. In order to meet TOP TIER Detergent Gasoline standards, a higher level of detergent is needed than what is required by the EPA. Also, TOP TIER was developed to give fuel marketers the opportunity to differentiate their product.

Why did the four automotive companies join together to develop TOP TIER?
All four corporations recognized the benefits to both the vehicle and the consumer. Also, joining together emphasized that low detergency is an issue of concern to several automotive companies.

What are the benefits of TOP TIER Detergent Gasoline?
TOP TIER Detergent Gasoline will help keep engines cleaner than gasoline containing the "Lowest Additive Concentration" set by the EPA. Clean engines help provide optimal fuel economy and performance and reduced emissions. Also, use of TOP TIER Detergent Gasoline will help reduce deposit related concerns.

Number: 01-06-04-022
Subject: Inaccurate/Erratic Fuel Level Gauge Readings (Install New Sensor, Strainer and/or RH Fuel Sender Assembly)
Model Year: 1997-2004 Chevrolet Corvette

Condition

Some owners may comment about inaccurate/erratic fuel level gauge reading conditions such as those indicated below:
Fuel gage suddenly drops to E (empty) and CHECK GAGES message illuminates (DTC P1431 or P0461 set).

Fuel gage does not go to F (full) after filling fuel tank.
Vehicle runs out of fuel while the gage still indicates fuel is available.

Cause

The conditions indicated above may be the result of one or a combination of more than one of the causes indicated below:
Stuck or intermittent sticking of the sensor float arm.
Clogged/restricted R.H. fuel sender assembly jet pump.
R.H. jet pump unable to transfer fuel due to fuel vaporization resulting in bubble accumulation in the fuel strainer.

Correction

Inspect the Julian date codes located on the bar code labels attached to the R.H. and L.H. fuel level sender assembly cover plates as shown in the figure.

If the R.H. sender date code is less/smaller than "01301", replace the complete assembly with a new fuel sender kit indicated below by model year. If the L.H. sender date code is less/smaller than "32791", replace the existing fuel sender sensor and strainer with those components contained in the applicable sensor and strainer kits shown below by model year.

To insure correct installation, follow the service procedure contained in the applicable Service Manual and the instructions contained in the service kits.
Parts Information
Part Number Description
88896043 R.H. Fuel Sender Kit (1997-1999 M.Y.)
88895126 R.H. Fuel Sender Kit (2000 M.Y.)
88899034 Fuel Sensor Kit (1997-2000 M.Y.)
12458245 Fuel Strainer Kit (1997-1999 M.Y.)
12459862 Fuel Strainer Kit (2000 M.Y.)

The problems due to the use of E10 gas.
In taking apart the RIGHT tank.

1. Screens get plugged up
2. Filter gets plugged up
3. Valve for transfer gets plugged up
5. Contact points for float/fuel level gets crap coating that effects hitting the electronic card contact wipers.
6. Contacts gets coated from E10 and prevent gas levels to be wrong.

Common with E10 gas and a cleaner will not clean all those clogged paths.

Deposit Control Standards

The standards developed by the four automobile manufacturers (BMW, General Motors, Honda, and Toyota) for TOP TIER Detergent Gasoline are described below. This technical document describes the deposit control performance of unleaded gasoline at the retail level that minimizes deposits on fuel injectors, intake valves, and combustion chambers. These standards comprise the requirements for TOP TIER Detergent Gasoline.

Standards

1.1 Retail Gasoline Performance Standards. The deposit control performance of unleaded gasoline conforming to section 1 of this document shall be met at the retail level in all grades of gasoline sold by a fuel company in all marketing areas of a selected nation. In addition, conformance to the standards shall mean gasoline sold in the selected nation shall not contain metallic additives, including methylcyclopentadienyl manganese tricarbonyl (MMT).

1.2 Deposit Control Additive Requirements. The deposit control additive used to meet the performance Standards described in 1.3 shall meet the substantially similar definition under Section 211(f) of the Clean Air Act. Also, the additive shall be certified to have met the minimum deposit control requirements established by the U.S. Environmental Protection Agency (EPA) in 40 CFR Part 80. Lastly, the additive shall be registered with the EPA in accordance with 40 CFR Part 79.

1.3 Deposit Control Initial Performance Standards. Initial deposit control performance shall be demonstrated using the tests shown below.

1.3.1 Intake Valve Keep Clean Initial Performance Standard.

1.3.1.1 Test Method. Intake valve deposit (IVD) keep clean performance shall be demonstrated using ASTM D 6201, Standard Test Method for Dynamometer Evaluation of Unleaded Spark-lgnition Engine Fuel for Intake Valve Deposit Formation. Tests demonstrating base fuel minimum deposit level (1.3.1.2) and additive performance (1.3.1.3) shall be conducted using the same engine block and cylinder head. All results shall be derived from operationally valid tests in accordance with the test validation criteria of ASTM D 6201. IVD results shall be reported for individual valves and as an average of all valves.

1.3.1.2 Base Fuel. The base fuel shall conform to ASTM D 4814 and shall contain commercial fuel grade ethanol conforming to ASTM D 4806. All gasoline blend stocks used to formulate the base fuel shall be representative of normal U.S. refinery operations and shall be derived from conversion units downstream of distillation. Butanes and pentanes are allowed for vapor pressure adjustment. The use of chemical streams is prohibited. The base fuel shall have the following specific properties after the addition of ethanol:

Contain enough denatured ethanol such that the actual ethanol content is no less than 8.0 and no more than 10.0 volume percent.
Contain no less than 8 volume percent olefins. At least 75% of the olefins shall be derived from FCC gasoline as defined by CARB (advisory letter, April 19, 2001).
Contain no less than 28 volume percent aromatics.
Contain no less than 48 mg/kg sulfur. At least 60% of the sulfur shall be derived from FCC blend stock.
Produce a 90% evaporation distillation temperature no less than 290?F.
Produce IVD no less than 500 mg averaged over all intake valves.
1.3.1.3 Demonstration of Performance. The base fuel from 1.3.1.2 shall contain enough deposit control additive such the IVD is no more than 50 mg averaged over all intake valves. Results for individual valves and an average shall be reported. The unwashed gum level of the fuel containing deposit control additive shall be determined according to ASTM D 381 and reported.

1.3.2 Combustion Chamber Deposit Initial Performance Standard.

1.3.2.1 Test Method. Combustion chamber deposits (CCD) shall be collected and weighed along with IVD using ASTM D 6201, Standard Test Method for Dynamometer Evaluation of Unleaded Spark-Ignition Engine Fuel for Intake Valve Deposit Formation. ASTM D 6201 does not contain a procedure for collecting and measuring CCD. Adapting a scrape and weigh procedure developed by CARB is recommended (see referenced test method dated March 12, 1999). Results for individual cylinders and an average shall be reported.

1.3.2.2 Base Fuel. Combustion chamber deposits shall be measured for the base fuel from 1.3.1.2.

1.3.2.3 Demonstration of Performance. The base fuel from 1.3.1.2 treated with additive at the concentration meeting the standard found in 1.3.1.3 shall not result in more than 140% of the average CCD weight for the base fuel without additive.

1.3.3 Fuel Injector Fouling Initial Performance Standard.

1.3.3.1 Test Method. Fuel injector fouling shall be measured using the TOP TIER fuel injector fouling vehicle test available from GM. GM will run the test on a first-come-first-served basis and shall make the method available to those who wish to run the test on their own.

1.3.3.2 Base Fuel. Two options for base fuel are available:

1.3.3.2.1 Option 1. A full boiling range hydrocarbon gasoline or gasoline blending component, without oxygenates and without deposit control additives, that results in at least five inoperative injectors when tested by the method in 1.3.3.1.

1.3.3.2.2 Option 2. Federal emissions test gasoline specified in DFR 86.113-04, into which 4-methylbenzenethiol (WARNING: Flammable solid; irritant) has been blended at a concentration of 56 mg/L. The blended fuel must result in at least four inoperative injectors when tested by the method in 1.3.3.1. the Federal emissions gasoline, without deposit control additives, available from Haltermann Products (1201 South Sheldon Road, Channelview, TX 77530; tel.: 800-969-2542) has been found to be satisfactory.

1.3.3.3 Demonstration of Performance. A demonstration of injector fouling shall be done first. At least five out of six injectors (with Option 1) or at least four out of six injectors (with Option 2) shall be inoperative for the test to be valid. A demonstration of additive performance shall be done after the fouling tendency demonstration; no other test shall be conducted on the vehicle in the interim. A demonstration of additive performance shall be conducted using the same vehicle (including the fuel drain and flush procedures and installing new injectors) with the same batch of base fuel, but now containing the same amount of deposit control additive as in 1.3.1.3. A pass is defined as no more than one inoperative injector.

1.3.4 Determination of Deposit Control Additive Performance Concentration.

1.3.4.1 Methodology. The concentration of deposit control additive needed to meet the standards in 1.3.1.3 and 1.3.3.3 should be equivalent. However, if the concentration of deposit control additive in 1.3.3.3 is grater than in 1.3.1.3m the higher value shall be regarded as meeting both standards. Also, if the difference between the two concentrations is grater than 15%, 1.3.2.3 shall be repeated using the higher concentration.

1.3.5 Intake Valve Sticking Initial Performance Standard.

1.3.5.1 Test Method. Intake valve sticking tendency shall be determined using either the 1.9 L Volkswagen engine (Wasserboxer according to CEC F-16-T-96) or the 5.0 L 1990-95 General Motors V-8 engine (SWRI IVS test). Two options are available for demonstrating intake valve sticking tendency.

1.3.5.2 Option 1. The valve-sticking tendency of the test fuel by itself will not have to be demonstrated prior to testing the candidate additive. The following shall be required of all tests:

Test fuel shall be either the same as in 1.3.1.2 or CEC valve sticking reference fuel.
Concentration of deposit control additive in the test fuel shall be at least twice the amount determined in 1.3.4.1.
Test temperature shall be -20?C.
Three 16-hr cold soak cycles, each followed by a compression pressure check, shall constitute a complete test.
1.3.5.2.1 Demonstration of Performance. A pass shall result in no stuck valves during any of the three cold starts. A stuck valve is defined as one in which the cylinder pressure is less than 80% of the normal average cylinder compression pressure.

1.3.5.3 Option 2. The valve-sticking tendency of the test fuel together with an additive known to cause valve sticking shall be demonstrated prior to testing the candidate additive. The following shall be required of all tests:

Test fuel shall be either the same as in 1.3.1.2 or CEC valve sticking test reference fuel.
An additive known to cause valve sticking shall be selected, and, when blended into test fuel, shall demonstrate valve sticking tendency as follows: (a) for the Volkswagen engine, at least two valves shall be stuck; (b) for the GM engine, at least three valves shall be stuck.
Test demonstrating performance of the candidate additive shall be conducted at a concentration that is at least three times the amount determined in 1.3.4.1.
Test temperature shall be -20?C.
One 16-hr cold soak cycle followed by a compression pressure check shall constitute a complete test.
1.3.5.3.1 Demonstration of Performance. A pass shall result in no stuck valves during the cold start. A stuck valve is defined as one in which cylinder compression is less than 80% of the normal average cylinder compression pressure.