<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>2204201 - Disclosure - Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Policies)</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

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</LabelSeparator><Level>2</Level><ElementName>us-gaap_UseOfEstimates</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>terseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="D2013Q2YTD" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;div style="font-family:Times New Roman;font-size:10pt;"&gt;&lt;div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-style:italic;font-weight:bold;"&gt;Use of Estimates&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;text-align:left;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;The preparation of financial statements in conformity with Generally Accepted Accounting Principles ("GAAP") requires the use of certain estimates by management in determining the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of sales and expenses during the reporting period.&amp;#160;&amp;#160;Significant items subject to such estimates and assumptions are the allowance for doubtful accounts receivable, valuation of inventory at lower of cost or market, valuation of goodwill and other intangible assets, and income taxes.&amp;#160;&amp;#160;Actual results could differ from those estimates. &lt;/font&gt;&lt;/div&gt;&lt;/div&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

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 -Publisher FASB

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</LabelSeparator><Level>2</Level><ElementName>us-gaap_RevenueRecognitionPolicyTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>terseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="D2013Q2YTD" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;div style="font-family:Times New Roman;font-size:10pt;"&gt;&lt;div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-style:italic;font-weight:bold;"&gt;Revenue Recognition&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;text-align:left;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;The Company derives its sales primarily from the services it performs and from the sale of processed oil from its used oil re-refinery.  Parts cleaning and other service revenues are recognized as the service is performed.  Product revenues are recognized at the time risk of loss passes to the customer.  The risk of loss passes to customers at various times depending on the particular terms of the sales contract in force with each individual customer.  Common thresholds for when risk of loss passes to the customer are at the time that product is loaded onto the shipping vessel or at the time that product is offloaded at the customer&amp;#8217;s receiving location.  Sales are recognized only if collection of the relevant receivable is probable, persuasive evidence of an arrangement exists, and the sales price is fixed or determinable.  &lt;/font&gt;&lt;/div&gt;&lt;/div&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>Disclosure of accounting policy for revenue recognition. If the entity has different policies for different types of revenue transactions, the policy for each material type of transaction is generally disclosed. If a sales transaction has multiple element arrangements (for example, delivery of multiple products, services or the rights to use assets) the disclosure may indicate the accounting policy for each unit of accounting as well as how units of accounting are determined and valued. The disclosure may encompass important judgment as to appropriateness of principles related to recognition of revenue. The disclosure also may indicate the entity's treatment of any unearned or deferred revenue that arises from the transaction.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

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 -Publisher SEC

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 -Name Accounting Standards Codification

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 -Publisher SEC

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</LabelSeparator><Level>2</Level><ElementName>us-gaap_BusinessCombinationsPolicy</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>terseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="D2013Q2YTD" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;div style="font-family:Times New Roman;font-size:10pt;"&gt;&lt;div style="line-height:120%;text-align:left;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-style:italic;font-weight:bold;"&gt;Acquisitions &lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;text-align:left;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;text-align:left;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;The Company accounts for acquired businesses using the purchase method of accounting, which requires that the assets acquired, liabilities assumed, and contingent consideration be recorded at the date of acquisition at their respective fair values.  It further requires that acquisition-related costs be recognized separately from the acquisition and expensed as incurred and restructuring costs to be expensed in periods subsequent to the acquisition date.  The Company records a preliminary purchase price allocation for its acquisitions and finalizes purchase price allocations as additional information relative to the fair values of the assets acquired becomes known.  &lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;/div&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>Disclosure of accounting policy for completed business combinations (purchase method, acquisition method or combination of entities under common control). This accounting policy may include a general discussion of the purchase method or acquisition method of accounting (including for example, the treatment accorded contingent consideration, the identification of assets and liabilities, the purchase price allocation process, how the fair values of acquired assets and liabilities are determined) and the entity's specific application thereof. An entity that acquires another entity in a leveraged buyout transaction generally discloses the accounting policy followed by the acquiring entity in determining the basis used to value its interest in the acquired entity, and the rationale for that accounting policy.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

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</LabelSeparator><Level>2</Level><ElementName>us-gaap_GoodwillAndIntangibleAssetsIntangibleAssetsPolicy</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>terseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="D2013Q2YTD" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;div style="font-family:Times New Roman;font-size:10pt;"&gt;&lt;div style="line-height:120%;text-align:left;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-style:italic;font-weight:bold;"&gt;Identifiable Intangible Assets&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;text-align:left;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;text-align:left;text-indent:24px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;The fair value of identifiable intangible assets is based on significant judgments made by management.  The Company may engage third party valuation appraisal firms to assist the Company in determining the fair values and useful lives of the assets acquired.  Such valuations and useful life determinations require the Company to make significant estimates and assumptions.  These estimates and assumptions are based on historical experience and information obtained from the management of the acquired companies and also include, but are not limited to, future expected cash flows to be earned from the continued operation of the acquired business and discount rates applied in determining the present value of those cash flows.  Unanticipated events and circumstances may occur that could affect the accuracy or validity of such assumptions, estimates, or actual results.  Acquisition-related finite lived intangible assets are amortized on a straight-line basis over their estimated economic lives.  The Company evaluates the estimated benefit periods and recoverability of its intangible assets when facts and circumstances indicate that the lives may not be appropriate and/or the carrying value of the asset may not be recoverable.  If the carrying value is not recoverable, impairment is measured as the amount by which the carrying value exceeds its estimated fair value. &lt;/font&gt;&lt;/div&gt;&lt;/div&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>Disclosure of accounting policy for intangible assets. This accounting policy may address both intangible assets subject to amortization and those that are not. The following also may be disclosed: (1) a description of intangible assets (2) the estimated useful lives of those assets (3) the amortization method used (4) how the entity assesses and measures impairment of such assets (5) how future cash flows are estimated (6) how the fair values of such asset are determined.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

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